The Reagan administration's decision to sell airborne warning and control system (AWACS) planes to Saudi Arabia foreshadows a grand defense strategy for the Middle East oil fields the congressional debate never confronted: an ambitious plan to build surrogate bases in Saudi Arabia, equipped and waiting for American forces to use.

The secret strategy, elaborated and pursued by officials in two administrations, would allow the U.S. Rapid Deployment Force to move "over the horizon" to these forward bases and pre-positioned supplies if the Soviet Union or other hostile forces attempted to capture the Persian Gulf oil fields, upon which America and other western nations depend.

U.S. air and naval forces, as well as the RDF, also could depend upon this military infrastructure if Middle East oil is in jeopardy.

In addition, the stage is set, according to an internal Pentagon paper and other sources, for a region-wide air defense network, led by Saudi Arabia and potentially including such moderate states as Kuwait, the United Arab Emirates, Oman, Bahrain and Qatar.

According to U.S. diplomatic and military sources, as well as an authoritative foreign official, the Saudi-U.S. arrangement has evolved during highly sensitive discussions over the last two years: a complex plan to help Saudi Arabia construct military facilities with a sophisticated electronic command system that could be the nerve center for U.S. forces fighting in defense of that nation.

The exact status of this understanding is not clear, but it appears to combine the hopes of defense planners on both sides with the reality of the initial transactions to advance the plan.

Though the overall plan has not been approved by the Reagan White House, the momentum of intricate plans developed by the Carter administration has continued.

To the extent that explicit terms have been agreed upon by the two governments, they were formalized in late February in a secret oral understanding between Maj. Gen. Charles L. Donnelly Jr., the chief of the U.S. military group in Saudi Arabia, and Col. Fahd Abdullah, the head of the Saudi air force and an influential member of the royal family, according to U.S. diplomats.

The plan allows U.S. and Saudi officials, in the absence of a formal diplomatic agreement, to deny particulars of the strategy while pursuing its many complicated steps. The Pentagon, asked to comment on this account, issued a blanket denial that there is any larger defense strategy for the region.

The controversial sale of five AWACS radar-surveillance planes is one small piece of what is envisioned, according to the official sources here and abroad.

The heart of the understanding is this: if America will sell the Saudis an integrated package of top-of-the-line military technology, Saudi Arabia will build and pay for a massive network of command, naval and air defense facilities large enough to sustain U.S. forces in intensive regional combat involving the Soviet Union.

The strategy is intended to deal with graduated threats ranging from local insurgencies to all-out warfare with a major outside power such as the Soviet Union, according to knowledgeable American and foreign sources.

Ultimately, according to the U.S. and foreign sources, the Saudis will permit the United States to "pre-position" more than a 90-day supply of equipment, munitions and supplies, including refined oil, in facilities constructed in Saudi Arabia by U.S. engineers according to U.S. specifications.

Many billions of dollars of this equipment will be paid for by the Saudis, but will match the war-fighting requirements of U.S. commanders.

As a key part of the understanding, the United States has agreed to provide a sophisticated command, control and communications (C3) system to interconnect a central command headquarters in Riyadh with six or more regional operations centers throughout the country.

The system will be able to tie the Saudis' F15 fighters, new AWACS planes, surface-to-air missiles, a countrywide net of ground radar stations and other equipment.

A portion of the C3 system was included in the AWACS sale approved last week, but the larger implications were never raised for the congressional debate.

"We are only obligated to tell them what is being sold. We are under no obligation to make them understand it," said a source who was involved in selling the AWACS package on Capitol Hill.

More significantly, it is understood that the Saudis would seek American assistance in a crisis. Then, the computerized command system would be able to coordinate a large-scale infusion of U.S. forces in an emergency.

In any case, the system will link an array of other sophisticated equipment, some of which the United States will lease or sell to the Saudis later and the rest of which the United States can simply plug into the Saudi C3 system.

Furthermore, sources say the Saudis have agreed to use the new technology to develop, with U.S. backing, an air defense system that goes far beyond the boundaries of Saudi Arabia to incorporate other moderate nations in the Persian Gulf region. The diplomatic negotiations, as well as some sales of military hardware, have begun in other gulf states toward that objective.

Asked for comment, Secretary of Defense Caspar W. Weinberger "flatly denies that the AWACS is the cornerstone of any larger program," according to Pentagon spokesman Benjamin Welles.

Maj. Gen. Richard V. Secord, deputy assistant secretary of defense for the Middle East, acknowledged that he and others had discussed with Fahd, "in general terms," the possibility of using the AWACS C3 system to link up a gulf regional air defense system, but he denied that there is any official plan to do so.

But Secord also made available to The Washington Post a Pentagon "issue paper," used to prepare administration officials for the AWACS debate, which said the AWACS sale "sets the stage for the development, with U.S. backing, of a regional air defense system for the entire gulf region."

Donnelly, now promoted and serving as U.S. commander in Japan, issued this statement in response to The Post's request for comment on his role in the secret negotiations:

"Lt. Gen. Charles L. Donnelly Jr., in his capacity as chief of the U.S. military training mission to Saudi Arabia, met regularly with Saudi officials to discuss numerous issues, including AWACS. The general has no further comment on your story."

All sources stressed that the Saudi government will retain full control and sovereignty over both its facilities and the advanced technology it will be purchasing.

In practical terms, however, the United States will maintain a technological veto over use of the advanced equipment, since such elaborate computer systems cannot function long without the presence of American technicians.

Nevertheless, the details of this long-term strategy are almost certain to alarm Israel further, deepening the concerns it expressed about the AWACS sale.

Reagan administration officials also said they believe that Israel would view the envisioned sharing of military data with other moderate gulf states as a precedent for eventual sharing with more hostile Arab states, a Pentagon official said.

The final arrangement, which will take years to complete, would overcome the well-recognized weaknesses of the U.S. Rapid Deployment Force, first created by the Carter administration.

From the start, Pentagon planners have acknowledged that the RDF has neither enough airlift capacity nor forward-based supply systems to be able to move troops and materials quickly to the Persian Gulf and fight a war of any duration in defense of the oil fields.

Other new U.S. facilities in the Middle East, including the one at Ra's Banas in Egypt, are a great distance from the oil territory that would have to be defended.

"People have alleged the RDF is built on sand," said former undersecretary of defense Robert Komer, the architect of the Rapid Deployment Force under President Carter. Komer was involved in developing the joint U.S.-Saudi strategy, but was unable to implement it.

The RDF, Komer said in an interview, "is built on sand if you don't have something like this in place. I see absolutely no other viable way to deter against aggression or defend Persian Gulf oil. And there is no other competent military judgment that I know of that there is another way."

The Pentagon "issue paper," prepared for the AWACS debate but not widely disseminated, says the "Saudis have indicated their desire to work toward an integrated regional defense system" that the United States has agreed to support. The paper said:

"Saudi Arabia has taken the lead in the formation of the Gulf Cooperation Council (GCC) with Bahrain, Oman, Qatar, UAE United Arab Emirates and Kuwait. A major objective of the GCC is to enhance the defense of the gulf. The AWACS and its ground environment system affords the capability to link the air defense networks of these states into the unified system."

If Middle East politics permit Saudi Arabia to organize an integrated air defense network of Arab states, Pentagon planners hope that the Saudis can go further and invite a permanent U.S. presence.

This would effectively create a new regional military alliance against the Soviet Union on its southwestern borders, complementing NATO defenses on the west, according to U.S. and foreign sources.

The handful of American and Saudi leaders aware of the overall strategy note that there are many intervening steps before the United States can expand the understanding to get anything equivalent to basing rights in the Persian Gulf.

However, in the meantime, the elaborate positioning of equipment and supplies and the likelihood that, in the event of a major threat, Saudi Arabia and its gulf neighbors would call on American forces combine to form a tremendous deterrent to Soviet adventurism, according to Komer and other U.S. sources who insisted on anonymity.

Although sources disagreed on how many of the other Persian Gulf states would be prepared to join a Saudi-dominated, regional air defense network, each stressed that the Saudis have decided to prepare for such a contingency by building a much more elaborate military infrastructure than needed for their own purposes.

Then, if and when their neighbors agree or an overwhelming crisis threatens the security of the gulf, the Saudis will have put the equipment in place and can call in their American ally.

Operating without the budgetary constraints of less wealthy nations, the Saudis have begun to spend defense allocations expected to total between $35 billion and $60 billion in the next decade, U.S. and foreign sources said.

"We have never had this degree of political and financial support from any nation before," one official said while confirming most details of the program.

From the Saudi point of view, America has chosen Saudi Arabia as its linchpin in a joint strategy to protect the gulf, both U.S. and foreign sources say.

The Saudis refer to the secret understanding as a "package deal," and have told U.S. officials repeatedly that it hinges on private assurances by U.S. officials that Saudi Arabia will be provided with air attack and intelligence capabilities that the administration has publicly told supporters of Israel are not promised.

From the point of view of high-ranking U.S. officials, the understanding is a cornerstone for building a new regional alliance capable of filling the vacuum left after America's premier military partner in the region, the late shah of Iran, fell in January, 1979, according to U.S. sources.

Planners here envision that someday the alliance also will include Egypt and will coordinate its military role in the region.

Sources disagree on what equipment has been guaranteed the Saudis specifically and under what circumstances it will be sold. But all sources agree that, while no one U.S. official has signed off on the entire list of Saudi requests, discussions with the Saudis have proceeded as if there were a package.

Both the Carter administration, under which a slightly less ambitious version of the strategy was developed, and the Reagan administration have been reluctant to talk openly about the full scope of the strategy for fear that supporters of Israel would oppose it even more strongly than they did the AWACS sale, according to one former Pentagon official.

" Israeli Prime Minister Menachem Begin wants to spoil U.S. security relationships with the Arabs to force the Arabs to come to terms with Israel on Israel's terms," the official said. "And Begin sees the long-term trend toward U.S. security relationships with Arab states as being at the expense of Israel's political security and eventually, maybe, military security."

Other present and former administration sources insist that the ultimate intentions were not discussed because of the Saudi royal family's sensitivity that it would be criticized at home and elsewhere in the Arab world for becoming too closely entangled with the United States.

"No country in the region is prepared to accept U.S. bases in peacetime," Komer said. "They are willing to let us provide all the technical assistance, design the systems, maintain them, support them, even operate them, but not under the American flag. We have got to fly their flag."

In any case, the administration decided that, rather than brief Congress on the full potential of the program, certain items could be presented to Congress as seemingly unrelated, according to informed diplomatic and defense sources.

In other instances, where no formal agreements have been signed with the Saudis, such as positioning of equipment, the administration decided it had no technical obligation to inform Congress in advance.

And in certain aspects of the larger plan, as in the case of the enormous construction projects already managed by the U.S. Corps of Engineer, no congressional approval is necessary.

In addition, the Pentagon has advised the Saudis to purchase other equipment directly from contractors and to break the orders down into individual acquisitions of less than the dollar limits required for notice to Congress: $7 million for certain weapons systems and $25 million for less sensitive equipment, according to both U.S. and foreign sources.

Still other equipment is being purchased by the Saudis from such other governments as England, France and Spain, and some of the acquisitions for the overall program are being made by other gulf state governments, sometimes at Saudi expense.

The larger strategy for U.S.-Saudi cooperation grew out of several developments. First, Mitre Corp., a research firm that does much of the Air Force's advanced electronics work, completed a two-year study for the Saudis in 1980, suggesting how the latest in computer technology could be programmed to coordinate Saudi air defenses and, if needed, all U.S. forces in the area.

Two other studies described how to coordinate Saudi land and naval forces and how to pull all three under one integrated command, control, communications (C3) system.

Defense officials have been keenly aware that U.S. military forces moving quickly into the gulf would be crippled without a coordinated air defense system and topnotch C3 facilities, which would be cumbersome to transport.

However, the United States could hook into a Saudi C3 system, even when not operating directly with the Saudis, and could get all the same data simultaneously transferred by satellite both to U.S. bases in the Indian Ocean and to the Pentagon.

The advanced C3 systems could do even more, particularly if they also integrate electronic intelligence information, creating a command, control, communications and intelligence system, known as a C3I system.

The backbone of such a C3I system is the computer hardware and software, involving the most advanced data processing and display techniques.

With this new technology, tommorrow's battlefield commanders will be able to calculate almost instantly the precise location of enemy ground, air and naval forces and to target them with the most efficient and effective battle plan from computer display consoles in a central command post, according to optimistic Pentagon planners.

Saudi Arabian and U.S. leaders hope that by 1990 this C3I system will link up other components of the program into an integrated combat network.

In addition to the computerized C3I capability, the other components will include the five AWACS aircraft, electronic-intelligence and electronic-warfare equipment the Saudis are now acquiring secretly through U.S. and foreign private sources, the Saudis' present fighter aircraft and missile network, new ground radars the Saudis are acquiring under the AWACS program and through other purchases, other arms the United States plans to sell or lease to the Saudis, a communications satellite specifically "dedicated" to the military program and the latest in automated command facilities.

When the Mitre study was completed in the summer of 1980, other Saudi arms requests were pending, including one for AWACS planes, and others for bomb racks for F15s and extra-capacity fuel tanks to extend their range, Sidewinder missiles and refueling tankers.

Congressional concern about providing such equipment to the Saudis had been made clear two years earlier, when the Carter administration narrowly won Senate approval to sell the Saudis 60 F15 fighters. But Carter administration planners believed that Congress might change its mind in view of other developments.

Since the previous winter, when the Soviet Union had invaded Afghanistan, military planners examining computerized simulations of a Persian Gulf war had concluded that all defense scenarios were doomed by the absence of adequately positioned bases in the region for the Rapid Deployment Force.

Beyond the usual logistical support, the planners found, combat in the Middle East or Southeast Asia is complicated by such considerations as inadequate access to fresh water supplies for troops and equipment, lack of access to refined oil and lack of adequate communications and transportation facilities.

Secondly, they had identified the shortage of transport planes with which to lift troops and support equipment as the principal bottleneck to effective RDF deployment.

The few facilities to which the Carter administration was arranging access -- Diego Garcia in the Indian Ocean, Bahrain, Egypt, Somalia, Kenya and Oman -- were, with the exception of the airfield at Bahrain, 500 to 2,300 miles from the critical points where U.S. forces would likely be deployed.

Although the Saudis had rebuffed initial discussions of American bases in the region, they were deeply concerned about Soviet intentions and were already building an $18 billion network of first-rate military facilities, using American contractors and specifications.

The question was American access. Donnelly and Fahd discussed selling the requested arms and creating a larger, integrated C3 system with which to coordinate the air defenses of the moderate gulf states.

By early fall of 1980, Prince Sultan, the Saudi defense minister, and Secretary of Defense Harold Brown had agreed through channels that Saudi Arabia would provide oversized "warehousing and infrastructure facilities" for "pre-positioning" U.S. equipment for the RDF.

In return, the United States would assist Saudi Arabia in acquiring the most modern C3 system and other equipment, such as AWACS and the bomb racks, if military studies found them to be the best solution for Saudi air surveillance and ground attack needs.

Fearing protests from Jewish groups similar to those that had accompanied the earlier decision to sell the F15s, the Carter administration agreed with the Saudis to put the issue off until after the 1980 election and to avoid discussing any plans to sell the Saudis equipment during the presidential campaign, provided that the Reagan campaign did not raise the issue.

The Saudis made indirect inquiries to the Reagan campaign and reportedly felt that they had an assurance that the issue would not be raised.

However, on Oct. 24, 1980, 11 days before the presidential election, in a move apparently designed to reassure the large Jewish voting population of New York state, President Carter announced that he would not sell bomb racks to the Saudis.

Prince Sultan, angry at Carter's statement, immediately put the pre-positioning arrangement on hold, and informed U.S. officials that he would cancel the 1978 order of 60 F15s, still on the assembly line. Two weeks later the president lost the election, including New York.

Faced with a pending security fiasco and a financial disaster for the St. Louis-based F15 prime contractor, McDonnell Douglas, Defense Secretary Brown and Secretary of State Edmund S. Muskie scrambled to repair the damage.

They assured the Saudis that they would recommend to the next administration that the Saudi needs be met by whatever equipment was decided upon in the pending airborne surveillance study and another pending study of air-to-ground attack needs.

The air-to-ground attack study was far enough along for the Saudis to know that the staff would recommend the F15 bomb racks. Prince Sultan withdrew his cancellation of the F15 order.

Then Muskie took the proposed sale items -- the C3 system, AWACS, Sidewinder missiles, fuel tanks, refueling tankers and the bomb racks -- to his designated successor, Gen. Alexander M. Haig Jr., and offered to have the Carter administration propose the program to Congress and take the initial heat from the Capitol Hill. Haig said the Reagan administration would prefer to evaluate the package for itself.

During February, with tacit U.S. encouragement, the Saudis took "the lead in the formation of the Gulf Cooperation Council (GCC)" with the moderate gulf states, Kuwait, Qatar, Bahrain, Oman and the United Arab Emirates, according to a Pentagon document.

The GCC began planning on how best to use its combined oil wealth to build a single coordinated military command. To encourage it further, the United States performed air defense studies for Bahrain, Oman and Qatar.

The United Arab Emirates and Kuwait have had similar assessments made recently. The Saudis also agreed to pay the cost of linking the air defense systems of these states into a single system.

The promise of this larger, region-wide system convinced the Reagan administration to move forward with the C3 package. By January the air surveillance study had indicated that the AWACS would require fewer ground radar stations than other alternatives.

In addition, the United States could use the AWACS information for its air defense needs should it move into the area in a crisis situation. The AWACS could be plugged into the air defense systems of the other gulf states if it were accompanied by a substantial C3 package.

In late February, Donnelly and Fahd resurrected their earlier understanding regarding pre-positioning and facility access, provided that the United States could come up with the promised equipment, according to State Department sources.

Because the understanding was so sensitive, it was handled through Pentagon channels with virtually no distribution in the State Department.

The message dispatched to Saudi Arabia from Washington told of the approvals, and said, "We recognize the necessity to provide an air-to-ground capability for the Royal Saudi Air Force," but that issue would wait until the pending study was completed.

U.S. Ambassador to Saudi Arabia John C. West interpreted the communique candidly for the Saudis: it meant they would get the F15 bomb racks, but probably not until after the 1982 congressional elections.

At the Pentagon, experts already had calculated how to install a C3 system capable of linking up all Saudi, U.S. and other regional forces. Early studies indicated that it could cost up to $5 billion to develop.

This would be difficult to explain to Congress as an individual appropriation, particularly where it involved future expansion to other gulf states, according to one fully briefed source.

The Saudis' C3 system is sufficiently large, Defense Department officials agree, that it can handle and deploy on multiple sorties all of their 60 F15s and more than 300 additional fighters, plus all the Hawk surface-to-air missiles in the region.

According to these well-informed U.S. and foreign sources, the larger strategy has several other facets which U.S. and Saudi officials have discussed and Pentagon officials are encouraging the Saudis to pursue:

* Additional C3 systems for the Saudi army and navy which could be combined with the C3 system sold with the AWACS into one master command, control and communications system.

* An option to allow the Saudis to lease the four U.S. AWACS aircraft presently in Saudi Arabia and keep them there after the five purchased AWACS arrive.

* Purchase through commercial sources of electronic-intelligence and electronic-warfare equipment of precisely the type the administration assured Congress would not be a part of the AWACS package. All will interlink to make the C3 system a command, control, communications and intelligence (C3I) system.

* An understanding that the United States will, "as circumstances dictate," continually upgrade the Saudi C3I system with electronic equipment not available on the commercial market. Discussions have taken place with the Saudis about providing them the Joint Tactical Information Data System, one of the items the administration told the Senate would not be provided along with the AWACS.

Construction or acquisitions which can be broken into pieces under $7 million each for a major weapons system or below $25 million each for other types of military equipment do not require congressional approval.

* Purchase through commercial channels of a satellite hookup for the C3I system, allowing it much greater flexibility.

* Training and special equipment for a combat-ready, quick-response Saudi mini-RDF directed against infiltrators and oil-field saboteurs.

* A specially designed detection system using remote-control sensors located to protect vital oil-field equipment.

* A secret Saudi plan to construct a series of hardened oil-storage facilities protected to withstand intensive bombing.

In order to protect these new and other existing oil facilities, extensive new naval port facilities would be built, capable of accomodating RDF and U.S. fleet needs.

* The United Arab Emirates, Kuwait and Qatar are shopping for billions of dollars worth of air defense and electronic-warfare equipment designed to link to the future Saudis system.

The UAE is purchasing radar and Hawk surface-to-air missile systems that are linkable with the Saudi equipment. The Pentagon considers the Saudis likely to "financially support upgraded air defense for Bahrain Hawk and ground radars , Qatar, Oman."

* U.S. options to link in an assortment of the latest U.S. technology available, including spy satellites, the SR71 Blackbird reconnaissance planes, carrier-based E2C surveillance aircraft. Under this option U.S. intelligence information would not be shared with the Saudis, but all information picked up by their C3I system would be available to the United States.