Page 23 of a secret 1984 U.S. study on the balance of military power in the Middle East -- intended to be the most authoritative judgment of the government's intelligence agencies -- draws this conclusion:

"Israel not only will maintain its current margin of military superi- ority over every combination of Arab forces, but will widen the gap during the next five years. Israel will be able to defeat any combination of Arab forces through the rest of the decade."

This military superiority, which U.S. intelligence officials say hasn't changed, is a direct result of the longstanding special relationship between the United States and Israel. Since 1970, the Israeli military has used $21 billion in U.S. grants and loans to buy the most sophisticated American weaponry or to pay for building its own.

More recently, friends of Israel in Congress have helped maintain that military edge in another way -- by blocking or reducing sales of U.S.-built military equipment to allied Arab nations.

Israel's supporters consider opposition to Arab arms sales to be an important test of congressional fidelity to the Jewish state, second only to support for the $3 billion annual aid package to Israel. Members of Congress who pass the test are the most likely recipients of campaign donations from pro-Israel political action committees ($3.6 million in 1984) and from individuals, according to interviews and fund-raising materials.

Congressional support for Israel has become so strong that some officials say they believe it has become the controlling factor in U.S. arms sales policy in the Middle East. Others say Congress is just filling a vacuum created as the Reagan administration has backed away from actively pursuing Arab arms sales.

In 1981, President Reagan saved a major arms package for Saudi Arabia by personal intervention; last year, two multibillion-dollar sales, to the Saudis and Jordan, were lost at the outset when administration officials failed to agree on a plan to push them through.

These recent events trouble some key officials, who see the United States shifting away from its longstanding policy of maintaining close ties to relatively moderate Arab countries as it tries to protect Israel's security.

Richard W. Murphy, assistant secretary of state for the region, told Congress last spring that it should reject the contention that U.S. policy in the Middle East "is a zero sum game, that ties with one side preclude friendship with the other . . . . Those notions are wrong and our experience proves that they are."

Referring to Congress' inclination to oppose Arab arms sales, Murphy added, "For the first time in three decades . . . recent events threaten to undermine our balanced approach" in the area. Study Delayed Saudi Package

A revealing case history of this apparent shift in U.S. foreign policy began with a White House meeting on Jan. 23, 1985. At that time, the Reagan administration planned to sell Saudi Arabia an arms package worth more than $3 billion, including 40 top-of-the-line F15 fighters, thousands of missiles and improved electronics for F15s already in the Saudi inventory.

Attending that White House session were then-national security affairs adviser Robert C. McFarlane, Secretary of State George P. Shultz and Defense Secretary Caspar W. Weinberger. McFarlane reported mounting opposition on Capitol Hill to the Saudi sale, and said it would be prudent to delay the proposal and conduct what came to be known as the MEAT (Middle East Arms Transfer) study of the impact of such sales on U.S. policy in the region, according to knowledgeable officials.

Weinberger supported the Saudi sale. A month earlier, he had hand-delivered a letter from Reagan to officials in Saudi Arabia that committed the United States to selling the F15s, according to Saudi and American sources.

Weinberger agreed to McFarlane's suggestion for a delay in hopes of using it to push a $2 billion arms package for Jordan, which would include advanced fighter jets and air defense missiles, knowledgeable sources said.

But the delay played directly into the hands of opponents, led by the American Israel Public Affairs Committee (AIPAC), who needed time. "Cap Weinberger had the Saudi sale in his pocket. It had already been approved by the president," recalled one official who was involved in the discussions. "But he took the chip out and put it back on the table in hopes of getting the Jordan sale, too. In doing so, he lost both."

McFarlane estimated that the MEAT study would take four to six weeks; it took six months. Some officials said the delay was intentional, a way to avoid confronting the issue. By the time the study was done, both packages were dead or dying.

AIPAC started the attack long before the administration announced its intention to sell the arms. It used a time-tested formula: Get inside information on the proposals, give it to the press or friendly members of Congress and use the resulting publicity to generate opposition.

After learning of the proposed sales, AIPAC's executive director, Thomas A. Dine, met with McFarlane and warned him that AIPAC wouldn't retreat from an all-out battle to prevent more F15s from being sold to Saudi Arabia. (In 1978, Congress approved the sale of 60 fighters after a lengthy and bitter fight.) Dine made AIPAC's position clear: No arms sales to any Arab country that hasn't made peace with Israel.

As Dine saw it, the timing was right for AIPAC and wrong for the administration. "They had other priorities. Contra aid. Tax reform," Dine said. "And they didn't want to go through another AWACS fight."

In fact, much of AIPAC's strength stemmed from that earlier deal to sell AWACS early warning radar planes to the Saudis, which the administration had narrowly steered through Congress in 1981. At that time, according to Dine, the organization had 8,000 members, 24 staff members and an annual budget of $1.8 million. Shaken and inspired by the AWACS defeat, AIPAC launched a vigorous membership and fund-raising drive. It now claims nearly 50,000 members, a $6 million budget, 80 staff members and offices in New York, Los Angeles, San Francisco and Austin as well as Washington.

The AWACS defeat also led to the proliferation of scores of pro-Israel political action committees. It spurred activists in the Jewish community to mount campaigns against members of Congress perceived as anti-Israel while attempting to elect more sympathetic politicians.

During this time, AIPAC sounded ever-louder warnings to its members and supporters on Capitol Hill about a growing threat to Israel from the arsenals of neighboring Arab states. American efforts to sell fighter planes to Saudi Arabia and Jordan was like "ringing Israel with a noose of American iron," warned Benjamin Netanyahu, Israel's ambassador to the United Nations.

In early February 1985, Sen. Alan Cranston (D-Calif.), a supporter of Israel, announced that he had collected the signatures of 63 senators on a letter to Reagan expressing "serious reservations" about any Saudi sale.

On March 20, Rep. Lawrence J. Smith (D-Fla.) attached an amendment to the foreign aid bill making any proposed Jordan sale contingent on King Hussein's willingness to recognize Israel and begin "direct negotiations." The measure angered the Jordanians, including Foreign Minister Taher Masri, who tried vainly to argue Smith out of the proposal over breakfast that morning at the Watergate Hotel. Even the wording was troublesome; in Arabic, "direct" negotiations would be interpreted as "separate" -- implying that Jordan was willing to make a separate peace with Israel, something that many Arab countries would not abide.

Jordan's lobbyist, Denis M. Neill, whose Washington firm represents several Arab countries, got the language changed to "negotiate directly" -- which is more vague and would allow Hussein more flexibility. It was a diplomatic nicety but an important one, said a Jordanian official.

Despite warnings from Congress, Reagan in May told Hussein at the White House that he would push for approval of a sale.

By late May, administration officials realized they could save the Saudi package only by jettisoning the bulk of it -- the F15s. They informed Bandar Bin Sultan, the Saudi ambassador to the United States.

Looking ahead, Bandar then requested and received a letter from Reagan that said generally that the president understood the Saudi need to shop for fighters elsewhere. The Saudis wanted the letter, according to two knowledgeable sources, because they suspected the administration would later blame them for steering their business away from American aerospace companies if they bought from another supplier.

Much of this took place out of the public eye and went unreported by the press. Conditions Imposed on Jordan

Meanwhile, the Jordan sale was in trouble, too. Despite Reagan's promise to Hussein, the administration did little during the summer of 1985. Then, on Sept. 27, Hussein tried to get the sale back on track during a speech at the United Nations, saying for the first time that he was willing to "negotiate directly" with Israel. Administration officials were pleased; three days later, Hussein made the rounds on Capitol Hill to lobby for the weapons.

But AIPAC and others were busy, too. The day after Hussein's visit to the Capitol, six House members signed a letter calling for further conditions, specifically that no arms could be sold to Jordan until negotiations between Israel and Jordan had begun. Three days later, six senators did the same.

On Oct. 7, the Italian cruise ship Achille Lauro was hijacked by Palestinian terrorists, further inflaming anti-Arab sentiment here. "Whoever said timing is 75 percent of politics is right," Dine said.

On Oct. 21, the administration formally sent the Jordan package to Capitol Hill, despite all indications that it would go nowhere. The next day, 74 senators sponsored a resolution to block the sale. Two days after that, the Senate upped the ante, delaying all action for four months unless "direct and meaningful" negotiations took place.

Hussein was angry. He referred to the addition of "meaningful" as blackmail. Lobbyist Neill said, "The king jumped one hurdle so Congress erected a wall." The Jordanian sale was dead.

"The cumulative effect of the American government inflicting public national humiliations on our moderate Arab friends is bound to have an adverse effect," said Nicholas A. Veliotes, who was assistant secretary of state for the region from 1981 to 1983 and then ambassador to Egypt until this spring.

But Cranston sees the issue as a legitimate battle between the president and Congress over foreign policy. "We specifically have a law that gives us Congress the power to veto an arms sale," he said. "It creates a misunderstanding elsewhere if we say that once a president makes a promise that's it as far as America goes. That's not the way America works."

Geoffrey Kemp, the Middle East specialist on the National Security Council from 1981 to 1985, said he felt AIPAC's successes may be making Israel more vulnerable in the long run. "They are getting their friends in Congress to vote against the very countries most likely to make peace with Israel," he said. "What's important is whether there will be any moderates left. How will AIPAC feel if Hussein or Fahd of Saudi Arabia is assassinated and replaced by a radical military junta?" Fighters Purchased From Britain

Meanwhile, the Saudis needed to find a replacement for the F15s that had been dropped from their package. Armed with their July 1985 letter from Reagan, the Saudis went to London and bought 72 Tornado fighters in September as part of a package estimated to be worth more than $12 billion.

Some defense experts contend that Israeli security is jeopardized more by the Tornado attack plane than it would have been by the F15, because the British put fewer restrictions on the Tornados' use than Congress did when it sold F15s to the Saudis in 1978, specifying that they could not be based on Saudi airfields nearest to Israel or be equipped with certain kinds of bomb racks.

Some U.S. officials said the Tornado sale hurt the United States, too. The U.S. aerospace industry lost lucrative contracts and potential new jobs; the U.S. military lost the advantage of having familiar equipment at Saudi bases, which might be needed in a confrontation involving Persian Gulf oil fields.

After the British sale was announced, two pro-Israel congressmen carried the fight across the Atlantic. Reps. Mel Levine (D-Calif.) and Benjamin A. Gilman (R-N.Y.) wrote a letter of protest to British Prime Minister Margaret Thatcher, complaining that Britain's decision had endangered Israel's security. Thatcher's reply included the same reasoning that the Reagan administration used in proposing the sale -- that Saudi Arabia is a moderate pro-Western country with a right to defend itself.

Levine said in an interview that Saudi Arabia's ability to get its arms elsewhere raises "a difficult question" for U.S. lawmakers who opposed the U.S. sale. But he said, "I don't think that means that Congress should acquiesce to a policy that we don't think is in America's interest."

Without the F15s, only fragments remained of the administration's original Saudi package. It still included $1 billion for Stinger and Sidewinder antiaircraft missiles and improved electronics for the F15s owned by the Saudi air force.

But after several consultations between Dine and Shultz, including a 90-minute session last Feb. 28, the electronics were tossed out and the proposed deal -- pared to $354 million worth of missiles -- was sent to Congress in early March.

On March 20, less than half an hour after the administration had lost the first key vote in the House on $100 million in aid to CIA-backed rebels, called contras, fighting the government of Nicaragua, Dine said to Shultz, "I have some good news for you."

AIPAC had decided, Dine said, not to fight the reduced Saudi arms package. AIPAC's new position baffled some allies on Capitol Hill and angered some Jewish organizations, such as the Zionist Organization of America.

In fact, AIPAC and its allies in the previous 14 months had so successfully gutted the package that there wasn't much left to fight; even the Israeli government didn't object to it.

On May 6, the Senate crushed the proposal anyway, 73 to 22, after a debate filled with references to how the Saudis provide money to the Palestine Liberation Organization and Syria, which U.S. intelligence officials and some congressmen criticize for supporting terrorism.

The House followed suit the next day. On May 20, Bandar, the Saudi ambassador, visited the White House and agreed to another cutback -- the removal of the Stinger missiles from the package, reducing it to $265 million.

On May 21, Reagan vetoed the bill opposing the sale. He needed 34 votes to prevent the Senate from overriding the veto and the White House twisted arms toward that end.

On June 5, the administration prevailed by a single vote. The message seemed clear, according to administration and congressional sources: Even with AIPAC on the sidelines for three months and the White House actively backing the Saudis, Congress was so pro-Israel that it would vote against an Arab arms sale almost as a reflex action.

"I like to think," Dine said, "we prepared the environment."

NEXT: The emotional side of the relationship