This is a crucial time for arms control. Experts in the arms control community see a window of opportunity for progress -- and a risk that the opportunity may be lost.
As Soviet and American negotiators prepare to return to the Geneva talks this month, the Reagan administration remains frustrated at Moscow's reluctance to put a concrete proposal on the table.
But arms control advocates believe that recent moves by the Kremlin are a clear signal it wants to strike a bargain with the United States: significant reductions in strategic nuclear arsenals in exchange for limits on the development of space-based defensive systems.
``The Soviets now are laying out the terms of a deal,'' says John Steinbruner, director of foreign policy studies at the Brookings Institution. ``The summit will probably be the last opportunity to create a breakthrough. If President Reagan rejects that, the Soviet Union will react accordingly. This is an unbelievably critical moment.''
Taken singly, Soviet signals and soundings in recent months may not give the administration cause for jubilation. But taken together, say experts, they suggest the Soviets are serious:
Soviet leader Mikhail Gorbachev this week indicated that Moscow is prepared to accept ``fundamental research'' on the President's antimissile defense program or so-called ``star wars.'' This reinforces earlier hints the Soviets will not insist on banning all research on space-based defense technology, but might permit a distinction between pure science and the building of prototypes or ``models or mock-ups.''
The Soviets on Aug. 6 began a moratorium on tests of nuclear weapons to last until January 1986. They said they would extend the ban if the US reciprocates.
At the recent round of arms talks in Geneva, the Soviet side informally broached the idea of cutting strategic launchers by 25 to 40 percent and of reducing nuclear ``charges'' by an unspecified percentage. Earlier in Moscow a high Soviet military officer told Rep. Stephen J. Solarz (D) of New York that Moscow's offer to cut nuclear forces applied to warheads as well as missiles -- a proposal which would move in a direction attractive to the US.
The Soviets have also suggested that no more than 50 percent of offensive nuclear forces could be in weapons of any one type. This would place constraints on Soviet land-based missiles, which concern Washington the most.
In a meeting with American senators this week, Mr. Gorbachev also promised ``radical reductions'' in strategic nuclear weapons if the US put limits on SDI.
Administration officials tend to play down these developments. The Soviet moratorium bid is viewed as a propaganda ploy. The hints about possible warhead reductions are deemed too vague: Officials say the Soviets at Geneva never mentioned aggregate numbers for warhead limits or specific percentages with respect to limits in each category of weapons.
But some arms experts say they think the Soviets have publicly and privately stated their case better than has the administration.
The US at Geneva has proposed that each side be limited to 5,000 ballistic-missile warheads and offered a trade-off between US bomber weapons and Soviet heavy intercontinental ballistic missiles (ICBMs). But it has not spelled out details, and it insists that all its work on SDI (Strategic Defense Initiative or ``star wars'') falls within the limits of the Antiballistic Missile treaty -- which the Soviets question.
``I'm encouraged by the degree of flexibility in the overall Soviet position,'' says Alton Frye, an arms expert at the Carnegie Endowment for International Peace. ``They clearly have a desire to focus on [space-based] technologies that can be detected and verified. We would need to erect complex restraints to make limits on these technologies effective. But Gorbachev has played a card.''
Deep suspicions appear to lie behind the positioning on both sides. Diplomatic and arms experts suggest that the Soviets have not been officially forthcoming at Geneva because Mr. Gorbachev may still be consolidating his power at home, because he may want to play his own hand at the summit meeting with President Reagan, and because the Kremlin is suspicious that the US is engaged in a game.
Also, the Soviets are trying to court American and European opinion. By making public pronouncements about their position, they hope to demonstrate their credibility as arms partners and pressure Washington.
In this connection the administration's determination to go ahead with testing of an antisatellite (ASAT) weapon is viewed by critics as counterproductive. The Soviet Union this week declared that, if the US proceeds with the test, it will end its unilateral moratorium on the testing and deployment of ASATs.
While the administration views its test as a catch-up exercise, many experts scoff at the idea. The Soviet ASAT system is deemed rudimentary. Arms experts are concerned that US test will simply spur the Soviets to develop a sophisticated system -- when Moscow had indicated it was prepared to dismantle the present crude one.