Soviet officials, apparently concerned about the toll their six-year-old military involvement in Afghanistan has taken, have begun to voice complaints about rising casualties and admitted to reporters that they are "not very happy" with the situation.

But U.S. officials say that whatever doubts Moscow has begun to voice publicly, they have said nothing of the kind in private.

In the face of a street demonstration here protesting, among other issues, Soviet involvement in Afghanistan and pointed questions from the western press about the war, Soviet officials may have softened the tone of their usually steadfast defense of the war in order to defuse tensions.

After six years of verbal cross fire, the Soviet Union and the United States have brought their quarrel over the Afghan war to the site of the first summit meeting between U.S. and Soviet leaders since Soviet troops first marched into Afghanistan in December 1979.

With a public appeal for "a political solution," Soviet officials here have projected a will to end the war. Toward that end, said Georgi Arbatov, director of the Moscow-based Institute for the Study of the U.S.A. and Canada, in an interview today, "the assistance of the United States would be most welcome." Arbatov said he meant that "the United States was not an onlooker" in Afghanistan, a reference to covert U.S. help for the rebels fighting the Soviet-installed government.

U.S. officials are urging Soviet officials to go beyond public laments over the war. "If they want some way to get out," Secretary of State George P. Shultz said in an interview with American television today, "it's easy to find it."

The exchanges precede the scheduled discussion Wednesday between President Reagan and Soviet leader Mikhail Gorbachev on regional issues, when Reagan is expected to broach the subject of Afghanistan.

In a speech at the United Nations in late October, Reagan identified regional conflicts involving Soviet or Soviet-backed troops as his main concern for the summit. In addition to Afghanistan, he referred to Ethiopia, Angola, Cambodia and Nicaragua.

Behind closed doors, U.S. officials here said, Gorbachev is unlikely to echo the urgent calls his aides have sounded for "a political solution" to the conflict. When Shultz raised the issue at a Kremlin meeting with Gorbachev two weeks ago, the w0106 ----- r a BC-11/18/85-SOVIET 1stadd w0106 11-18 A17 turn toward openness about a war that the Soviets used to treat as a taboo topic.

In reaction, White House press spokesman Larry Speakes said in a briefing this morning that Afghanistan is on the summit agenda but that "we are not quite sure what the Soviet position will be."

The Soviets have not discussed a political solution with U.S. officials in private, national security adviser Robert C. McFarlane said in a news conference for the international press here today.

Outside the center, where another Soviet briefing on arms control was held today, the wife of imprisoned Soviet dissident Anatoly Scharansky, Avital Scharansky, stood before a sign reading "human rights lead to arms control."

The presence of outside protesters reinforced the issue of the Soviet human rights record, which Reagan plans to raise in the talks.

A recently released Soviet dissident, Irina Grivnina, carrying press credentials for a Dutch magazine, interrupted questions about arms control and shouted claims of human rights abuses and engaged in a heated exchange with Kremlin press spokesman Leonid Zamyatin.

Grivnina was jailed for 13 months in a Moscow prison and exiled for another 20 months in Soviet Central Asia for her work in publicizing Soviet use of psychiatric hospitals to confine political prisoners.

In their briefing yesterday, Soviet officials referred to indirect talks between Pakistan and Afghanistan as the vehicle for reaching a political solution.

U.S. officials say that Moscow's failure to present a timetable for troop withdrawal has stymied the talks.

"If they withdraw all those troops," White House Chief of Staff Donald T. Regan said on CBS' Face the Nation today, "a political solution would be entirely possible."

Asked what future the Soviet Union envisions for Afghanistan, one Soviet official said yesterday, "It should be neutral, nonaligned, and a friendly state to the Soviet Union."

Deputy Soviet spokesman Albert Vlasov, in discussing Afghanistan yesterday, said Moscow also feared conflicts in the Middle East, Central America and Africa could "detonate explosions with worldwide consequences." On the Middle East, he said the Soviet Union would join any international conference that included the Palestine Liberation Organization.