The Soviet Union may be readying a further lure for Washington's Western allies to join in early European arms-control talks, European diplomats here suggest.
West German Foreign Minister Hans-Dietrich Genscher and his aides were given apparent hints to this effect during Mr. Genscher's recent visit to Moscow, the diplomats say.
The forum for the Soviet diplomatic move, if and when it comes, would be the current conference on East-West detente in Madrid. That often-stormy parley has just recessed until early May.
Moscow seems to be weighing a further softening of its position on a West European proposal at the conference for extending so-called "confidence-building measures" to the entire European part of the USSR, diplomats say. Such confidence-building measures include advance notification of military maneuvers.
The report from diplomats here follows a generally low-key Western response to a high-profile Soviet bid to revive detente, beginning with a major speech by President Leonid Brezhnev Feb. 23.
The Soviets have since moved to play down somewhat their proposal for an immediate freeze on nuclear missile forces in Europe, seen in the West as merely cementing Soviet superiority in that area.
Clearly concerned over plans to base new US missiles in Western Europe starting in 1983, the Soviets have been stressing instead the benefits for Western Europe of another proposal: early talks on control and eventual reduction of current missile forces.
But that strategy, reflected in an April 7 speech by Mr. Brezhnev in Prague, hasn't worked, either.
The Nuclear Planning Group of NATO, which began talks in Bonn as Mr. Brezhnev spoke, issued a generally stern communique rapping the Soviet missile buildup and reaffirming Western determination to answer in kind.
The Brezhnev speech had also sought to untie his arms proposals from Western pressure for Soviet restraint on the Polish crisis. But an agreed statement read out after the NATO talks linked prospects for arms accords to Soviet behavior in Poland.
While delivering a scolding assessment of the NATO meeting, the official news media have increasingly been stressing the importance of the talks in Madrid.
The Communist Party newspaper Pravda April 12 spoke of "obvious progress" in Madrid and said, "US effort to turn the forum into an arena of psychological warfare and confrontation are turning into a fiasco." The authoritative newspaper said, "There are real possibilities for securing a conclusion of the meeting marked by adoption of positive decisions."
Among these, Moscow has consistently stressed, would be the convening of a conference on European disarmament.
One condition for West European agreement to such a parley has been Soviet willingness to extend the zone of East-West "confidence" measures to the European part of the USSR, up to the Ural Mountains hundreds of miles inside its western frontier.
In his Feb. 23 speech to the Soviet Communist Party congress, Mr. Brezhnev surprised some Moscow diplomats by agreeing to that idea -- with one catch: that "the Western states, too, extend the confidence zone accordingly."
Diplomats initially took this to mean inclusion of parts of the US, not exactly "European" and a clear nonstarter from the West's point of view.
Mr. Genscher tried to find out just what the Soviets had in mind, at one point reportedly gibing at Soviet Foreign Minister Andrei Gromyko, "Come on . . . you know, after all, that you can still get us from behind the Urals."
Mr. Genscher is said to have stressed that inclusion of US territory in the European confidence-building equation was out of the question.
The Soviet side, diplomats here say, replied that it was up to the West to suggest some kind of trade-off for the Soviet concession, not specifying what Moscow had in mind.
But at a luncheon during the Genscher visit, Mr. Gromyko seemed to soften -- or at least generalize -- Soviet language on the issue, stressing the need for a "balanced nature" in such an accord rather than specifically for widening of the Western confidence zone.
The Genscher party is said to have told fellow diplomats that it got the impression from various Soviet officials that Moscow might be thinking in terms of extending confidence measures to some portion of Atlantic Ocean air or sea space.
Some European diplomats are interpreting the hedged Moscow response as an indication the Soviets might not even insist on that, but instead want simply a token Western concession for a point on which it is in their interest to yield.