The United States and the Soviet Union today concluded a seven-week round of talks in Geneva on limiting nuclear and space weapons that produced the first signs of progress toward an interim accord since the negotiations opened a year ago.

The two sides exchanged new proposals that showed some convergence toward reductions in medium-range missiles based in Europe. But there was no substantive change in positions in the other two forums on intercontinental nuclear missiles and space-based defensive systems, according to U.S. negotiators and allied officials informed about the talks.

"Our verdict is a mixed one," U.S. delegation head Max Kampelman said after the final session. He said that while both sides moved toward such common aims as a separate accord on intermediate-range missiles, adequate verification measures and the ultimate goal of banishing all nuclear weapons, there was "less accomplished than we had hoped."

Chief Soviet negotiator Viktor Karpov blamed the Americans for the failure to make more headway. "We introduced a lot of proposals here," he told reporters. "We hope maybe next time there will be more progress than this time."

The Soviet and U.S. delegations are expected to return to their capitals for a two-month recess before resuming negotiations on May 8.

Senior American delegates said they perceived some cause for optimism in that for the first time in the year-old talks, Soviet negotiators formally confirmed a desire to reach a separate accord eliminating U.S. and Soviet intermediate missiles from the European zone that would not be tied to parallel agreement in the other two areas.

Karpov said today that the new Soviet offer calling for the removal of all U.S. and Soviet missiles from the European zone was "a proposal that can be agreed right away, so it depends upon the United States to agree on that and rid Europe of Soviet and American missiles right now."

The Americans, citing allied concerns in Europe and Japan, objected to several key conditions in the Soviet proposal, including a freeze on British and French nuclear arsenals, a ban on the transfer of nuclear arms and no reductions in the mobile Soviet SS20 missile force in Asia.

In a counterproposal Feb. 24, the United States called for the elimination within three years of more than 200 U.S.-built Pershing II and cruise missiles now in Western Europe and more than 400 SS20s now deployed in the European and Asian sectors of the Soviet Union.

The United States also sought to ease West German anxieties by demanding withdrawal of Soviet short-range SS22 and SS23 missiles based in East Germany and Czechoslovakia. While Soviet negotiators have not responded, Foreign Minister Eduard Shevardnadze said in a speech to the Soviet Communist Party congress that Moscow would be willing to remove those missiles in order to consummate an agreement.

This round opened Jan. 16, the day after Soviet leader Mikhail Gorbachev unveiled a sweeping three-stage plan to eliminate all nuclear weapons by the year 2000.

U.S. negotiators said they saw nothing new in the Soviet call in the first stage for 50 percent cuts in strategic nuclear arsenals, a goal that Gorbachev and President Reagan agreed upon at the Geneva summit meeting last November. Nor have the Soviet negotiators relented in their opposition to the testing and deployment of what they call "space-strike weapons" -- Reagan's research program into space-based defenses.

The deadlock over space-defense systems had impeded progress in the talks on strategic and intermediate missiles until Gorbachev indicated last fall that Moscow might be prepared to seek a separate accord on medium-range missiles and sever linkage to other categories.

But Soviet negotiators refrained from advancing this concept until the latest round, when they formally proposed eliminating U.S. and Soviet missiles in the European zone.

Washington Post correspondent Celestine Bohlen reported from Moscow:

As the round of arms talks ended, Soviet Col. Gen. Nikolai Chervov charged in a press conference that the United States has shown that its negotiating position has not changed "one iota" since 1981.

Chervov said Soviet negotiators "even using a microscope, had not been able to detect anything new or constructive" in the U.S. response to the Jan. 15 Soviet initiative.

Gorbachev told the party congress last week that the U.S. response was disappointing. But Soviet officials said he had had little time to review the U.S. position in detail.

Today, Chervov said the view taken by Gorbachev had been "confirmed at this time due to clarifications made in Geneva." He said that the Soviet Union moved toward compromise by separating the question of medium-range missiles from other arms control negotiations.

"We have also compromised on nuclear arms of Britain and France," he said.