Moscow and Washington are at a spring-loaded impasse on arms control. Neither superpower wants to give the other the advantage in negotiating position or public perception. Yet each has strong reasons to reduce advanced weaponry and keep the prospects for progress here a strong possibility.
This was most clearly shown in the weekend flurry of offers and counteroffers regarding strategic nuclear weapons and military activity in space. And no matter what the outcome of this latest exchange, both sides have taken significant steps that could at least increase the possibility of a breakthrough in the stalled arms control talks.
Moscow, while it hesitates to do anything that would enhance Ronald Reagan's reelection bid, has - on the eve of the US presidential election - given the President a chance to demonstrate earnestness and flexibility on arms control. This caught many Washington observers by surprise.
''It is unexpected,'' says William Kincade, executive director of the Arms Control Association, a private organization. ''All conventional wisdom has been upset.''
For its part, the Reagan administration has considerably softened its official position on bilateral talks about weapons in space in a way calculated to allow both sides to save face and at least rekindle broader discussions on nuclear weapons.
Arms control advocates see this as an important - if still elusive - opportunity they hope will not be lost.
''Both sides have an interest in appearing to be willing to negotiate,'' said a former senior arms control negotiator. ''We certainly ought to take the opportunity to talk, but it's so hard to tell whether this is posturing for the electorate or a serious change of mind.''
And as chief US strategic arms negotiator Edward Rowny said recently, ''A wide gulf still separates the United States and the Soviet Union in several fundamental areas.''
The Soviet Union, through its official news agency, said yesterday it finds ''totally unsatisfactory'' Washington's desire to link talks about banning weapons in space with negotiations on nuclear weapons. It was on Friday that Secretary of State George P. Shultz received from Soviet Ambassador to the US Anatoly F. Dobrynin, word of Moscow's interest in September talks on antisatellite (ASAT) weapons and ballistic missile defenses known here as ''Star Wars.''
US officials responded with unusual quickness, accepting the Soviet offer but adding that they wanted to use the Vienna forum to talk about ''mutually agreeable arrangements'' under which the strategic and medium-range nuclear weapons talks in Geneva could be resumed.
At the same time, US officials were careful to stress that this was not a prerequisite for meeting in Vienna, that there were ''no preconditions.'' This, in essence, left it up to the Soviets to respond.
In doing so, Moscow chose to read the American counteroffer as conditional on reopening Geneva's subject matter. The Soviets broke off the INF (intermediate-range nuclear forces) talks when NATO began deploying Pershing II and cruise missiles in Europe late last year. And they have refused to set a date for the next round of talks on strategic (intercontinental) nuclear weapons.
The timing was incidental, but the Soviet Union launched another satellite the same day it announced its invitation to talk about antisatellite
weapons and ballistic missile defenses in Vienna.
The Kremlin, understanding that it trails the US in the advanced technologies applying to space warfare, is trying to head off this fall's planned testing of a small, aircraft-carried rocket that could threaten Soviet satellites (of which there are many more than US satellites). Like the US, the Soviet Union is becoming increasingly reliant on satellites to monitor fleet movements, missile testing, and troop activities.
The recent successful testing by the US of an antimissile rocket able to intercept a warhead in space made clear that the United States is well able to carry aggressive military space technologies from theory into practice.
The Reagan administration is in the delicate political position of mistrusting Moscow's offers, yet not being able to reject them outright.
The administration is under unusual pressure from Republicans as well as Democrats to make some progress on arms control. Several of its key military programs - the MX missile and ASAT weapons - are tied to arms control restraints in congressional budgeting.
For example, even the milder Senate version of the defense authorization bill would forbid ASAT testing against a target in space until 30 days after the President had certified that ''the United States is endeavoring to negotiate in good faith the strictest possible limitations . . . consistent with the national-security interests.'' The latest Soviet offer would seem directly keyed to this point.
Meanwhile, the White House continues to find itself criticized for pressing ahead with the futuristic, space-based ballistic missile defense called for in the President's controversial ''Star Wars'' speech 15 months ago.
In an interview with the Los Angeles Times last week, former President Richard Nixon said that even advanced missile defenses could be overwhelmed by attacking nuclear warheads.
And he said that if the United States is going to press ahead with such research, it ought to share it with the Soviet Union so that neither side could feel confident about being able to launch a successful first strike.