President Carter is deciding this weekend whether officially to inform the Soviet Union that the United States may dig thousands of new holes to permit deceptive basing of America's land-based intercontinental ballistic missiles, government sources have revealed.
After months of internal debate, the Carter administration has decided to move toward multiple-hole basing as the best way to assure the protection of America's land-based missiles into the 1980s, informed sources said.
The potential vulnerability of these missiles has concerned defense planners and inflamed domestic critics of the new strategic arms limitation talks (SALT) agreement being negotiated with the Soviet Union.
Carter's senior advisers reportedly agreed last Wednesday to recommend to Carter that Secretary of State Cyrus R. Vance pass the word to the Soviets that the United States may opt for the multiple-hole basing system in the early 1980s. They suggested Vance do this next Wednesday or Thursday in Geneva, where he is scheduled to meet with Andrei A. Gromyko, the Soviet foreign minister.
Another option the president could choose would be to have Paul C. Warnke, the chief U.S. SALT negotiator, inform his Soviet counterpart in Geneva that the United States is leaning toward the new basing system.
Some officials fear that the Soviets may react negatively to any American move of this kind perhaps jeopardizing the SALT process. Other officials contend that the administration must make this move both to assure protection for land-based strategic missiles and to assure domestic critics - before completion of new arms pacts with the Soviets - that the administration will take no risks with the land-based missile force.
The principal purpose of the Vance-Gromyko meeting is to continue discussions on the new SALT agreements. If Carter agrees to his aides' recommendations. Vance will indicate that the United States regards the multiple-hole system as a proper option in the period after the expiration of a three-year protocol that is expected to accompany the new SALT pact.
That protocol contains a previously agreed-to ban on all forms of mobile land-based missile systems. Administration officials have agreed, sources said, that the plan for basing missiles in fields of new holes would be, in effect, a mobile missile system.
The idea for such a basing system has been pushed by Paul H. Nitze, a strategic arms negotiator in the Nixon administration and a leading hardline critic of the Carter administration's strategic arms policies. Administration officials privately expressed hope that a decision to begin development of the system could win Nitze's support for the new SALT agreements Administration strategists say Nitze's backing could help ensure congressional approval of the agreements.
Nitze said in an interview that a decision to go ahead with the system could solve the most serious problem he sees in the new SALT agreements, but he declined to pledge his support for the entire package at this time.
Several senior officials predicted in interviews that the defense budget for fiscal 1980 - to be submitted to Congress next January - will contain funds to begin development of the new basing system, which is known as "MAP," for multiple aiming points.
MAP would allow live missiles to be moved at random in a field of empty holes, thus making it much harder for Soviet planners to target on U.S. missiles with their own ICBMs. The Washington Post reported the Pentagon's new interest in MAP 10 days ago.
The multiple aiming points would be the holes, which are known as "vertical shelters" in the vernacular of arms specialists.
The system could be used with Minuteman III missiles. Later it could be used with a new MX supermissile if the administration decides to build one.
Some senior administration officials oppose the MAP idea as potentially dangerous because it could invite a whole new round in the arms race that could result in a less stable strategic balance with the Soviet Union. Other officials argue forcefully that these concerns are misplaced.
Sources on both sides of the argument emphasized that no final decision has been made to deploy a MAP system, and that such a decision might never be made. However, the administration's senior officials have decided that the United States must now have the option to build MAP in the early 1980s both to answer the arguments of domestic SALT critics like Nitze and to try to ensure the invulnerability of U.S. land-based missiles in the event the Soviets initiated a sneak attack on them.
Several administration sources said the Soviets might become alarmed at the prospect of the United States preparing a MAP system for testing and deployment soon after the expiration of the new protocol. "There's danger that the Soviets will say 'oh, no,'" as one put it.
The Pentagon and Defense Secretary Harold Brown have reportedly argued that there is no need to tell the Soviets of American plans, since the United States does not intend to do anything that would violate the terms of arms agreements being negotiated.
Some officials have argued that a decision to deploy an American MAP system would be an invitation to the Soviets to deploy one of their own, raising a host of new potential dangers in the future.
In arms control terms, MAP raises unusual verification problems. The idea now favored in the government, for example, would be to dig perhaps 10 holes for each of about 400 ICBMs, each hole a mile or more from every other one in the same "field." The live missile and its launching mechanism would be moved by truck or rail from hole to hole under cover of night or in some other way that would prevent Soviet spy satellites from "seeing" where the missile was actually based at any given moment.
However, existing and proposed SALT agreements set a numerical limit on the number of land-based missiles each side can have, and the agreements also stipulate that both countries will not try to hide their missiles, so the spy satellites of each can keep count of the other's missiles.
So, U.S. officials acknowledge, some way would have to be found to assure the Soviets that the United States really has, for example, nine empty holes for every full one, and not 10 missiles hidden away in the new holes. U.S. officials have discussed various ways of doing this, ranging from periodic, brief removal of the tops of all the holes, allowing Soviet satellites to confirm that the proper number are indeed empty, to provisions for on-site inspection by the Soviets.
U.S. officials express confidence that ways can be found to convince the Soviets that the United States is not maintaining more than the allowed number of missiles, despite the new holes.
But some officials express concern that the Soviets might not be equally cooperative in the future if they built a MAP system.
One official predicted, for example, that five or 10 years from now domestic hardliners might be arguing that the Soviets are cheating in a MAP program by keeping more holes filled than they were supposed to.
Another potential danger, some officials fear, is that a decision by the United States to deploy this kind of mobile missile system would lead the Soviets to use other types of mobile systems, producing a new contest in the development and deployment of entire new generations of missiles.
"It will end up being another cost of SALT," one arms control advocate said, suggesting that the arms negotiations themselves continue to open doors to new arenas of arms competition between the superpowers.
But a combination of political concerns and determination to preserve the theoretical invulnerability of U.S. land-based ICBMs has apparently prevailed over these fears in the administration, at least for the time being. Some officials privately held out the possibility the deployment of a MAP system might be avoided in the future through new negotiated agreements with the Soviets or some unforeseen technological development.
Senior administration officials decided many weeks ago that President Carter would have to have some response to Senate critics' arguments that continuing improvements in Soviet capabilities would raise the possibility by the mid-1980s that a Soviet attack could wipe out America's land-based missile force.
Many officials have argued that the United States maintains missiles on submarines and bombers for just such an eventuality, and others dispute the whole idea that a rational Soviet leader would risk massive destruction of his country to achieve whatever marginal advantage might come from wiping out America's land-based missiles.
But critics said the Soviets might exploit a future superiority for political purposes, and added that U.S. security depended on the usability of all three of its nuclear strike forces - land-based and sea-based missiles and the bombers.
Administration strategists decided they could not dismiss those arguments, even if they didn't agree entirely with them. A search then began for an adequate response.
The Ford administration's plan for meeting this challenge was to build a new MX supermissile and base it in long underground tunnels. The missile would move back and forth in the tunnel to elude Soviet targeters.
But during the past year Pentagon analysts - until recently enthusiasts for this plan - concluded that it would not work, because a tunnel hit by an enemy nuclear weapon would probably be unable to protect a missile anywhere inside it.
So the Carter administration had lost the option it inherited from its predecessor. When the administration then decided that it had to have a new program to win Senate approval of new SALT agreements, a search began for a new way to protect land-based missiles.
MAP emerged at the best option in the view of most administration officials. However, a number of practical questions about its feasibility have been raised - reportedly by Carter himself, among others - and officials assert that a decision to go for MAP is still some distance in the future.
The Defense Science Board it studying at least one other alternative a plan to put large missiles on vehicles that would travel constantly along grids of highway built inside U.S. military bases.