As the debate on MX continues, attention has been drawn increasingly to the question of the value of this weapon in arms control negotiations, and it now appears that in both the House and the Senate members will soon have a chance to make a constructive contribution to that discussion. Respected members of both parties are proposing a U.S.-Soviet pause in the flight-testing of new MIRVed ICBMs, our MX and the parallel Soviet SS-X-24. These proposals deserve strong support. In discussing them I will also try to set the record straight on the views of Andrei Sakharov.

The first and most important reason for considering the flight-test pause is that unless it is useful for arms control, MX-in-Minuteman is plainly a dangerous and expensive blunder. The current debate shows already that Rep. Les Aspin is right when he tells us that he and the Scowcroft Commission made a political miscalculation in supposing that this system could be the centerpiece of a new consensus. The narrowing margin in the House and the sharpened debate in the Senate show plainly that the harder these bodies look at MX-in-Minuteman, the less they like it.

The reason for this result is both simple and basic: this weapon in this basing mode is a bad system by longstanding American standards. It is a vulnerable, destabilizing, obsolescent system that violates the first rule of American strategic weapons procurement--one laid down by Dwight Eisenhower and followed (except for the blunder of MIRVing) by every president until Ronald Reagan: that any new strategic system should add to the overall survivability of our basically second- strike forces. Because Aspin and the Scowcroft Commission decided to overlook this elemental defect (well known to them all), they presented a compromise that is losing ground simply because it lacks merit. Good compromises like the Social Security package come out of reciprocal concessions that permit real progress toward agreed goals, not out of a sudden decision to call a bad scheme a good one.

It is no wonder, then, that as this system has become better understood, the architects of the compromise and the president himself have shifted their emphasis to the arms control issue. MX-in- Minuteman may be destabilizing, but without it how can we get Moscow to dismantle its own destabilizing SS-18s and SS-19s? Certainly any new system does have some bargaining value. The crucial question is how much?

So far the administration has firmly maintained that the right course is to deploy MX as a counter to the big Soviet missiles, and not to trade it except at a most improbable price. As Kenneth Adelman wrote to the Senate, in words approved by the White House, "Unless the Soviets are prepared to reverse this buildup and forgo their heavy and medium ICBMs, the U.S. will go forward with MX." None of Reagan's assurances of his deep commitment to arms control has yet modified this preposterous position by one syllable. It is high time for Congress to give him some good advice.

In this context the idea of a flight-test pause has great force. First, it would make real the merely verbal priority so far accorded to arms control. It would make plain the readiness of this country to find a better use for MX-in-Minuteman than its deployment.

Second, the proposal is timely. No weapons system has ever been given up to arms control by either side after it was fully tested--at least not until it was dying of old age anyway. Once MX is deployed, only its further deployment is likely to be considered negotiable.

Third, the pause is both verifiable and mutually advantageous. Each side knows when the other tests, and each side has much to gain by avoiding new solid-fuel MIRVed ICBMs deployed by its adversary. Weapons builders habitually neglect this interest, but political leaders should do better.

Fourth, the proposals can be so framed as to leave ample flexibility to the president. There is nothing in the pause itself that prevents the search for a wider bargain that might indeed bring reductions in the large destabilizing Soviet systems. Such a wider bargain is obviously needed for the long run.

Let me turn now to Andrei Sakharov's magnificent letter to Sidney Drell. I had the privilege of serving as the intermediary between Sakharov's friends and the editor of Foreign Affairs in offering that letter for publication. It is not only one more demonstration of Sakharov's extraordinary courage, but also another proof of the power of his imaginative intelligence. It deserves better treatment than the out-of-context quotation of a single phrase in favor of MX, itself carefully qualified by the word "perhaps."

Sakharov does indeed see MX as a possible bargaining chip, but he also recognizes two realities that the administration so far does not. First, he sees that the best time for a bargain is before deployment. "Indeed, that would be best of all." Second, he knows that MX alone cannot be traded for any large part of the Soviet ICBM force. In the sentence following the one quoted by Aspin and others, he says:

"But, at the same time, if the Soviets, in deed and not just in word, take significant verifiable measures for reducing the number of land-based missiles (more precisely, for destroying them), then the West should not only abolish MX missiles (or not build them!) but carry out other significant disarmament programs as well."

Until the administration can tell us, at least in outline, what other weapons it is prepared to trade in this context, its supporters should have the fairness to quote Sakharov in full or not at all. There is much else that is important in Sakharov's letter. He knows what large-scale nuclear war would be like, and says so with matchless clarity; he knows also how unpredictable the upshot will be if even one nuclear weapon is used, and so he is against the first use of these weapons by anyone; he favors a Western conventional buildup; he is "highly doubtful" about the prospect of an effective defense against missiles; he passionately reasserts the critical importance of Niels Bohr's "openness of society" and of human rights. He also warns against Soviet propaganda and is skeptical of the freeze. But he does not attempt, as Americans must, to weigh the relative merits of particular kinds of American modernization, and that is one reason more why one should not read his conditional approval of MX, written in February, as unconditional support for MX-in-Minuteman in July.

Sakharov does one thing more that has special relevance in the context of proposals for a flight- test pause. He emphasizes the "enormous importance" of arms control negotiations:

"They must be conducted continuously--in the brighter periods of international relations but also in the periods when relations are strained--and conducted with persistence, foresight, firmness and, at the same time, with flexibility and initiative."

Bipartisan proposals for a joint pause in flight- testing show just this "flexibility and initiative." Their passage will not bind our chief negotiator on the terms of any eventual agreement, but it will send him a message that he badly needs to hear.