The case of Andrei Sakharov and Yelena Bonner dramatizes the central question of our nuclear age:

How are two nations which hold the fate of the world in their hands to relate to one another when their ruling value systems stand at diametrically opposing poles?

During the past 15 years, two sharply contrasting U.S. policies have emerged. The Nixon-Ford-Kissinger administration practiced what Richard Nixon aptly called "hardheaded d,etente." Its tools were trade and other forms of cooperation, combined with discreet pressure applied as part of a process of continuing negotiation.

Although it produced considerable flexibility for lateral movement, "hardheaded d,etente" could not last as an American policy for the same reason it held so much appeal to the Soviet leadership: it lacked moral content. Its goal was world order in the classic European sense. It was suspicious of internal forces for change that threatened established ruling elites -- in the Soviet Union, Chile, wherever.

Jimmy Carter remedied that defect with a vengeance. He placed human rights at the center of his policy toward the Soviet Union and repeatedly "punished" (a word he favored) the Soviets for morally unacceptable behavior. The tools employed by Carter to administer punishment were, to a considerable extent, the various components of the web of interdependencies developed by Nixon-Ford- Kissinger.

Under Ronald Reagan, that moralistic emphasis reached an apex with the description of the Soviet Union as the "focus of evil," as relations between the superpowers deteriorated and the arms race accelerated.

Which approach is preferable? Each, in my view, contains serious deficiences. A policy in tune with American values and interess requires both moral concern and tactical flexibility, both calculation and compassion.

One way to serve American values and interests at once would be to establish cooperative activity as an overriding national objective to be pursued with calculated sophistication and moral determination. This policy would replace the prevailing vacillation between no contacts and an uncritical pursuit of contacts, which the Soviets exploit by limiting their participation to party hacks. It would set strict standards for cooperation and push them hard.

A policy of aggressive cooperation would recognize that the chief enemy is less world communist ideology, which takes many evolving forms (China, Hungary, Yugoslavia), than it is the repressive Soviet police state, which is compulsively hostile to any evolution at all, communist or otherwise.

Instead of responding to repugnant Soviet behavior by cutting off contacts as "punishment" (which actually makes work easier for the police state apparatus), we would keep up the pressure, constantly pushing for new and expanded contacts of substance in the teeth of Soviet repression. Our principal target would be the emerging scientific and technical elite, the most sophisticated and cosmopolitan segment of Soviet society, who enjoy the highest status, upon whom the totalitarian power structure depends for running the system.

In pursuing that target, we could expect much more support than now from our European and Japanese allies, who already favor increased cooperation and greater flexibility in dealing with the Soviets.

Would such a policy legitimize Soviet policies of repression toward Sakharov, Bonner and others? On the contrary, it would constitute the strongest and most effective rejection of those policies. The Soviet police apparatus thrives on isolation. Why assist its efforts? Under present conditions, whenever they want to tighten the screws at home, they need only create an incident. We have handed them flexibility at our expense. In an important sense, American policy has made itself hostage to the KGB.

A policy of aggressive cooperation might best be launched with a proposal to do something big with the Soviets. It must be a long-term undertaking that locks them into an expanding program of joint activity. Soviet policy makers must find it sufficiently appealing to stay in, although it places their reactionary system of internal controls increasingly at risk.

One promising possibility is an international manned mission to Mars in the 21st century. It could be put forward as an alternative to competing Star Wars space weapons systems, which would otherwise be developed in the same time frame.

Unlike Star Wars, it requires no technology breakthroughs and thus would be far less costly. Unlike Star Wars, which would polarize scientific inquiry on the greater frontier of space, it would mobilize the world's best scientists and engineers in a common endeavor on behalf of all humanity. Unlike Star Wars, it would mandate ever greater openness across an expanding front, to the thriving benefit of democratic values and interests. And unlike Star Wars, our allies would welcome it with relief and excitement, for it would be a response to the greatest problem of our time that is wholly in tune with the best in the American character.

Joint activity on a grand scale would respond to the deepest aspirations of Andrei Sakharov. In the late 1960s and early 1970s, Sakharov sought to nudge the Soviet Union in preciselythat direction. Then the police apparatus moved in and re-established the "us" versus "them" condition upon which it thrives.

"Any action increasing the division of mankind, any preaching of the incompatibility of world ideologies and nations is madness and a crime," Sakharov wrote. With such utterances, his descent from official favor began, until, alone and isolated, he could retain his integrity only by lashing back at his captors.

But we should not confuse his entrapped response with the deep universal spirit that moved him to seek the intellectual freedom which must inevitably ensue from expanded communication and joint activity on an international scale. We have it in our power to resurrect that noble spirit. All we need is the will and determination -- and the leadership.