THE SOVIETS AND THE SUMMIT : Break Seen in Talks on Conventional Forces : Arms control: Moscow’s negotiators have responded favorably to U.S. proposals, State Department officials say. The progress is mostly on minor issues.

The first signs of a break in the East-West impasse on reducing conventional forces in Europe have come in “constructive responses” by Soviet arms negotiator Viktor P. Karpov to earlier U.S. suggestions, State Department officials said Tuesday.

The progress toward eliminating obstacles to an agreement in the so-called CFE talks, coming on the eve of Soviet President Mikhail S. Gorbachev’s arrival in Washington, involves relatively minor matters--such as deciding the size of artillery weapons and armored personnel carriers to count under ceilings of the proposed treaty, the U.S. officials said.

Karpov also brought to Washington several new and “amorphous” ideas for resolving more difficult differences on aircraft and troop ceilings, the officials said. But both sides agreed that these issues would be left for President Bush and Gorbachev to negotiate at meetings that begin Thursday.

There were also hints that the North Atlantic Treaty Organization is prepared to make a key concession on troop ceilings. The Soviets want to establish such ceilings for both NATO and the Warsaw Pact in the CFE negotiations under way in Vienna.

According to U.S. and West European sources, NATO would be prepared to pledge to negotiate such limits immediately after a conventional forces accord is completed. The current treaty, meanwhile, would limit only U.S. and Soviet forces in the “central zone” of Europe at 195,000 for each nation, with the United States allowed an extra 30,000 on the periphery of the Continent.

A senior Bush Administration official, however, was less upbeat than State Department officials about the pre-summit talks between Karpov and State Department Undersecretary Reginald Bartholemew. He told reporters that “not much” progress had occurred on CFE issues and that “where progress has been made, it’s been hard, hard slogging.”

The official said that the Soviets had not yet provided answers to U.S. proposals on conventional forces in Europe. Most of the Karpov-Bartholemew talks have dealt with nuclear weapons--the strategic arms reduction talks that are near completion--rather than with the conventional forces negotiations, he said.

But another Administration official confirmed the account provided by State Department officials. And two Soviet spokesmen in Washington for the summit were optimistic about the prospects on CFE and the related issue of German membership in NATO after unification.

Gorbachev has expressed flat opposition to such membership, and last week he said that the Soviet Union would reassess its plans to withdraw its troops and enter into arms agreements if a united Germany is part of NATO’s military structure.

A key Soviet foreign policy adviser, Vitaly Churkin, retreated somewhat from Gorbachev’s remarks, saying that “it’s not our intention at all to slow down arms control talks--conventional or any other arms control talks.” Churkin, an aide to Soviet Foreign Minister Eduard A. Shevardnadze, also said that “there is a way to work out the German issue--its membership or non-membership in NATO.”

In addition, Georgy A. Arbatov, head of a Soviet think tank on the United States, indicated that manpower ceilings on a unified German army could be decided in future negotiations rather than in the current CFE negotiations.

The various comments seemed to herald the prospect for significant progress on conventional forces in Europe during the summit, although it still is not certain that a CFE treaty between NATO and the Warsaw Pact can be completed before year’s end as hoped.

Both Bush and Gorbachev will have to consult with their respective allies on any common ground reached during their discussions here and formal proposals must be submitted for consideration at the Vienna negotiations.

But any understandings reached by the leaders of the two alliances would be difficult for their allies to resist. They would provide major impetus toward German unification, toward further cuts in conventional and nuclear arms in Europe and toward efforts to devise a new security system for the Continent in the post-Cold War era.

Bush and Gorbachev are certain to sign a framework agreement outlining the final shape of a START treaty that will cut offensive nuclear arsenals by one-third to one-half, as well as lesser arms agreements on chemical weapons and nuclear testing limits.

The planned reductions in conventional weapons and troop levels in Europe are considered more significant and immediate in their impact. The cuts would reduce the danger of conventional conflict much more than the START treaty would reduce the risk of nuclear war, according to government officials and non-government experts.

The CFE talks became deadlocked earlier this year, presumably because the Soviets wanted to reevaluate their security posture in Europe after the crumbling of the Warsaw Pact and the seemingly certain prospect of a united East and West Germany.

Earlier this month, Secretary of State James A. Baker III took to Moscow a package of U.S. “ideas” intended to explore Soviet flexibility and give the negotiations new energy. The Soviets listened closely and asked detailed questions, officials said later, but did not engage in concrete discussions on the issues raised.

The ideas covered all of the five weapons categories--tanks, personnel carriers, artillery, helicopters and fixed-wing aircraft--as well as verification issues such as the number of on-site inspections of military bases and the destruction of withdrawn equipment.