BOTH the Soviet leadership and the Reagan administration are showing a new and welcome restraint in their public rhetoric as next month's summit approaches. The moderation shown in Washington as Mikhail Gorbachev lofted his latest arms control proposals may well be an early sign that the administration is prepared to talk seriously with the Soviets about major arms reductions. If Mr. Gorbachev is willing to be realistic and reasonable about striking a deal on offensive and defensive weapons which wor ks for both sides, the current impasse on arms control could be broken. However, one key arms control goal for well over two decades remains curiously absent from current discussions. That is a comprehensive ban on nuclear explosions. An end to nuclear explosions could be an invaluable underpinning in efforts both to reduce nuclear arms and to deal with space weapons -- the goals at the current negotiations. In fact, the survival of any agreement resulting from those negotiations may depend on a test ban, since vigorous programs of new weapons development could place an int olerable strain on either side's willingness to live with constraints on existing arms.
The test-ban issue received a boost last summer when Mr. Gorbachev announced that the Soviets would observe a unilateral moratorium from early August through December. The Soviet leader also invited the United States to join in a bilateral moratorium to extend past December. The President seemed initially attracted to the idea, although the White House later seemed much more dubious. Nonetheless, the President indicated a willingness to engage in a mutual moratorium after our ``necessary'' testing is co mpleted.
Early last month, I and other members of a Senate delegation had an opportunity to discuss the Soviet offer with Mr. Gorbachev. The Soviet leader argued strongly for his proposal, maintaining that a joint moratorium would permit a return to the negotiating table to set the terms of a comprehensive ban. Moreover, he said, a halt in testing would stop the creation of new weapons and existing arsenals would become obsolete as they aged.
Mr. Gorbachev has a point, and we ought to test his seriousness. Specifically, we need to establish what verification provisions would apply; and we need to be assured that, despite Gorbachev's words, a moratorium would not substitute for a formal agreement. A nonbinding pause of uncertain duration is no substitute for a detailed set of long-term agreed commitments with effective provisions for verification.
A moratorium of a finite duration, however -- such as one year -- would open the way to a resumption of the negotiations on a formal agreement conducted by the Carter administration. Considerable progress on verification matters had been made in these negotiations. The sides had agreed to allow seismic monitoring stations on their territory, and details on inspections on demand to look into suspicious seismic activity were being worked out. Thus, the two sides would not be starting from scratch. A finit e duration to a moratorium would give the sides reason to conclude their work expeditiously, although, if success were in sight, there would be nothing wrong with a brief extension of the moratorium.
Critics argue that a moratorium should be avoided, because the Soviets might break out of it, as they did the moratorium that preceded the Limited Test Ban Treaty of 1963. That concern is based on an erroneous recalling of the record. From 1958 until August of 1961, both sides observed a testing moratorium, although President Eisenhower announced in 1959 the US would no longer be bound, thus opening the way to a similar Soviet decision. The Soviets had said they would not remain bound if any Western pow ers tested. After four French tests the Soviets resumed testing, and the United States followed suit. I conclude that this record should give us heart to try a moratorium, rather than the reverse.
The President's advisers may well believe that certain tests are necessary before a moratorium. Such a view could be a smoke screen to conceal opposition to any constraints on the development of new weapons, but it could also be associated with the laudable goal of developing more-stable systems, such as the single-warhead Midgetman. If it is the former, the President should be honest and say that he cannot live with a moratorium or a test-ban treaty. If there are solid reasons to conduct some tests, su ch as stability, the President should direct the bureaucracy to develop a revised testing schedule that could be completed within a matter of months.
With that schedule and a rationale for it in mind, the President should propose to Mr. Gorbachev at the summit a date for the commencement of a moratorium. If feasible, some verification steps which both sides could readily accept and which would not require protracted negotiations could be made part of the moratorium. These could include inspections upon demand and preparation for the employment of seismic stations when agreement on a formal ban is reached. At the summit, the two leaders should a lso agree upon a date for the early resumption of negotiations on the test-ban treaty.
As the Senate has indicated, the President should also seek Senate advice and consent to ratification of the still unratified 1974 and 1976 treaties. The Threshold Test Ban Treaty (TTBT, 1974) restricts tests in the only medium in which nuclear tests are allowed -- underground -- to 150 kilotons. A companion treaty -- the Peaceful Nuclear Explosions Treaty (1976) -- was designed to ensure that so-called ``peaceful'' explosions were not used as a way to test and gain weapons information outside the
strictures of the TTBT. In addition, a ratified Threshold Ban could serve as the basis for a decision to sharply reduce the threshold to a radically lower level of, say, one kiloton -- which noted seismologists believe to be a verifiable level -- if progress toward a complete ban becomes stalled.
The Threshold Test Ban Treaty and the Peaceful Nuclear Explosions Treaty can be verified with high confidence. Recent advances in seismology are helping resolve questions about compliance and reassuring us that we can ratify those treaties without threatening our security.
Weapons laboratory chiefs have indicated that they can meet their responsibilities under these constraints.
If President Reagan is serious in his professed desire to eliminate nuclear weapons from the face of the earth, he must start somewhere; and Mr. Gorbachev has presented a potentially promising opportunity. But what specifically could we reasonably expect to achieve through a temporary moratorium followed by a longer-term comprehensive test ban?
Over time, confidence in the reliability of our warheads would erode, although actual reliability should remain high for some time.
Eventually, however, the reliance placed on nuclear weapons by both sides would decline, and that would be to everyone's benefit.
A moratorium followed by a ban would curb the modernization of US and Soviet nuclear warheads. This could prevent them from developing new, smaller warheads with high weight-to-yield ratios to be proliferated on their missile forces, especially MIRVs. It could also impede the development of new technologies, such as X-ray lasers driven by nuclear explosions.
A moratorium and ban would put pressure on the Chinese and the French to stop their testing programs.
Such steps by the superpowers would serve to reinforce the resolve of the 127 nations who have forsworn nuclear weapons. A ban open to all nations could well give new life to the effort to stop the nuclear arms race.
There is no question that problems must be overcome if these controls on testing are to be achieved. Mr. Reagan and Mr. Gorbachev both recognize the problems. I believe that they can recognize, also, the possibilities. If so, in a matter of weeks a new course could be set which would leave us all more secure.
Sen. Claiborne Pell (D) of Rhode Island, the ranking Democrat on the Committee on Foreign Relations, is cochairman of the US Senate Arms Control Observer Group.