Soviet President Yuri Andropov announced new arms control proposals tonight to demonstrate Soviet "flexibility" but said categorically that the Geneva talks will collapse when U.S. medium-range nuclear missile deployments in Western Europe get under way.

In an apparent bid to induce a delay in the U.S. deployments, which are scheduled to start in December, Andropov said that the talks would continue if the United States "renounced the deployment of its missiles in Europe within the announced deadlines."

Andropov disclosed that Moscow is now prepared to cut down to "about 140" the number of its triple-warhead SS20 missiles in the European theater. This, he added, "is noticeably less" than the combined number of French and British nuclear delivery systems.

Previously the Russians have insisted on retaining 162 SS20s, or the total number of French and British systems.

Andropov reaffirmed his earlier assertion that Moscow would "liquidate" all other missiles in the European theater if an agreement were to be reached at Geneva. Tonight he went a step further by asserting that no new SS20 missiles would be deployed in the Asian part of the country if agreement were reached at Geneva.

Moreover, the Soviet leader asserted that he was prepared to show "additional flexibility" on the question of medium-range nuclear-capable aircraft. He said Moscow did not want to "undercut" the United States on this issue despite the fact that the Soviet Union did not have similar aircraft in third countries capable of reaching the United States.

The package was interpreted by western specialists here as containing both "cosmetic" changes and substantive ones.

In Washington, arms control officials told Washington Post staff writer Michael Getler that Andropov's apparent willingness to freeze missile deployments in Asia seemed to be a step forward in that it recognized, at least in principle, the frequently expressed American concern that these weapons need to be limited in Asia as well as in Europe.

But the officials noted that Andropov still had not dropped his insistence that no U.S. missiles be allowed in Europe, where the Soviets under his proposal would be allowed to keep 140 SS20s, each with three nuclear warheads. And the Soviet leader, officials here said, was still unwilling to drop his demand that Moscow be compensated for the sovereign British and French forces.

The U.S. officials said they could not comment on Andropov's proposal regarding aircraft because there were no details.

The timing of Andropov's proposal was significant, as it comes at a time of divisions within the western alliance over the American invasion of Grenada. It also coincides with a series of antinuclear demonstrations in Western Europe and presumably was designed to increase pressures on West European governments to seek a delay in U.S. deployments.

But the subtle substantive shifts appear to have been designed to precede next month's scheduled West German parliamentary debate on the deployment questions and at the same time to calm fears generated in China and Japan over a possible SS20 buildup in Asia.

Speaking in an interview with the Communist Party newspaper Pravda, Andropov rejected a view held in the West that the Russians would begin to negotiate in earnest in Geneva once the American Pershing II and cruise missiles are deployed.

He described such views as "an utter deception designed to damp the intensity of the struggle by the West European peoples against the appearance of American nuclear missiles in Europe."

"Everything must be totally clear here," he continued. "The appearance of new American missiles in Western Europe will make a continuation of the present talks in Geneva impossible. On the other hand, the Geneva talks can be continued if the United States does not start the actual deployment of the missiles." In buttressing his claim of Soviet flexibility, Andropov said that the Soviet Union has completely phased out its SS5 single-warhead missiles. He said a delay in U.S. deployments and the continuation of the Geneva talks would permit Moscow to "commence already now the reduction of our SS4 missiles--and we have more than 200 of them--and complete their liquidation in the course of 1984-85."

The figure of "about 140" SS20 missiles Moscow proposes to retain would involve 420 nuclear warheads, or the same number in the possession of France and Britain.

The tone of Andropov's interview was unusually conciliatory. The strongest words addressed to Washington were that the American position at Geneva was "unrealistic and lopsided" and that the Reagan administration was trying to gain military superiority over the Soviet Union.

Andropov's new proposals had been expected here, but it was believed that they were to come somewhat later. Diplomatic observers here said Moscow apparently decided to float them at this time to exploit the negative impact of the Grenada invasion in Europe and elsewhere.

According to these observers, the Russians are not expecting a sudden change in Reagan's position. Rather, Andropov's combination of cosmetic and moderate substantive changes was seen as aimed at West European audiences.

In contrast to his previous pronouncements and those made recently by senior military officers, Andropov today made no mention of Soviet countermeasures.

According to western sources, Moscow has about 355 SS20 missiles deployed as part of its medium-range force. Of this number, 251 are said to be stationed in the European theater and the rest in Siberia, presumably targeted on China and Japan.

Today's interview was an elaboration on an earlier Soviet proposal calling for mutual East-West reductions to 300 medium-range delivery systems on both sides. Under that proposal, the United States would be allowed to field 37 medium-range nuclear-capable aircraft in Europe (the other systems permitted would include the 162 British and French systems and 101 other NATO nuclear-capable aircraft.)

In a somewhat ambiguous phrase, Andropov said, "We have no aim to impinge on the United States." He said Moscow was prepared to "show additional flexibility and establish for NATO and the Soviet Union equal levels of medium-range delivery aircraft in a mutually acceptable quantitative range."

He added that "the concrete totals of these levels could be agreed upon just like the composition of the delivery aircraft--subject to limitations to be specified."