Today's surprise announcement of the withdrawal of some Soviet Army units from Afghanistan is a gesture calculated to help the Kremlin's damaged world relations at little real cost to itself.

Although one semiofficial Soviet source suggested the withdrawal shows Soviet good faith and shifts responsibility for a possible political settlement to Washington and the West, there is no evidence of any basic change in the Kremlin's unyielding position on its intervention.

The gesture is aimed at other targets: the squabbling Western allies meeting at the Venice summit, the wavering Moslem nations that have condemned the invasion, the anxious East Europeans, and Moscow's own boycott-impaired Summer Olympics.

From the start, Moscow's conditions for a settlement have not been altered.

The basic Kremlin demand requires an end to "outside aggression" against the Barbrak Karmal Marxist government prior to any full troop withdrawal. By this, Moscow means an end to the spontaneous Islamic based tribal rebellion against Kabul, which was intensified when Soviet troops arrived in force in December. This is a revolt that Washington has never controlled.

In recent private contacts with Western diplomats, the Soviets have flatly ruled out a total troop withdrawal simultaneous with Western nonaggression guarantees. This is because such a move would in all likelihood mean the downfall of the Babrak government, which cannot survive without Soviet arms.

This East-West impasse is unaffected by today's 36-word Tass dispatch from Kabul carried by major Soviet newspapers today. It announced that some unneeded Soviet Army units "are being withdrawn to Soviet territory" by mutual agreement between Moscow and Kabul.

The careful wording underlines Moscow's related withdrawal precondition: diplomatic recognition of the Barak government as the legitimate government of Afghanistan.

It is in this delicate area that today's Soviet probe for better relations may have the most impact. More than a million Afghan refugees have fled the strife in their homeland into neighboring Pakistan and Iran, which, like most other nonaligned Moslem countries, have refused to recognize the Babrak government since the Dec. 27 Soviet invasion.

Although Moslem countries have called strongly for the Soviets to withdraw and spurned a May initiative from Kabul for a regional settlement conference with Iran and Pakistan, nervousness among these nations on the Soviet periphery has increased noticeably over the months. Sources here said the troop withdrawal further complicates their position, leaving the Kremlin open to argue that since the Soviets have made a move to ease the crisis, the Moslems should extend recognition as a sign of good faith. The Kabul government has established its own justification for pursuing both atheist social reform and tolerance of Islam in an effort to appeal to other Moslem nations.

Pakistan so far has done little to curb insurgent activities in the crowded refugee camps just over the Afgan border. Islamabad is in an especially isolated position, suffering from bad relations with Moscow, bitter relations with Washington and deep fear of India, which just signed a $1.6 billion arms deal with the Soviets. The Soviet move would appear to increase the weight of these circumstances.

Although the Soviets have not said how many soldiers are being withdrawn, Moscow is likely to quickly try to fan anti-U.S. feelings in the Third World if the West fails to produce a positive response.

Despite today's unanimous declaration at the Venice summit that the withdrawal must continue until all Soviet troops are gone, the gesture is one that East and West Europeans have been advocating as a way to restore the atmosphere, if not the substance, of detente.

Significantly, the French were quick to assert that the withdrawal was the fruit of last month's Warsaw meeting between Soviet leader Leonid Brezhev and French President Valery Giscard d'Estaing, which so irritated Secretary of State Edmund Muskie at the time.

The move is reminiscent of October's withdrawal of 20,000 troops and 1,000 Soviet tanks from East Germany as part of an unsuccessful Kremlin effort to stall the NATO nuclear missile improvement decision. The Soviets have sharply criticized Washington since for rejecting the initiative out of hand. Brezhnev is sure to argue this point when West German Chancellor Helmut Schmidt arrives here June 30.

The Soviet media already is drawing attention to the Afghan withdrawal in the same way it did with the East German pullouts. Soviet television, which provided little coverage of the invasion, broadcast an interview tonight with a tank officer who said his unit is leaving after a friendly and successsful stay. The Tass agency carried positive comments gathered from around the world on the withdrawal, including a dispatch from Beirut suggesting the United States should reciprocate by pulling back some of its Indian Ocean forces.

The Soviet media effort is also aimed at more than a dozen nations that have not yet decided whether to join the U.S.-led boycott by about 50 nations of the Summer Olympics. The Games open here July 19. Some informed sources believe the Soviets put off a long-expected spring-summer offensive against the Afghan rebels in fear it would further damage the attendance at the Games. Moscow has labeled the boycott effort a failure.

Soviet sources said today they believe Foreign Minister Andrei Gromyko will explain the move in some detail at a closed-door Commuist Party Central Committee plenum expected to take place Monday. The Supreme Soviet (parliament) is scheduled to meet Tuesday to ratify the Central Committee's decisions.

There has been intense speculation in the foreign community that the Central Committee may make some changes in the ruling 14-member Politburo. Defense Minister Dmitri Ustinov, 71, a close Brezhev confidant, has not been seen in public since early April. There are persistent rumors he is seriously ill and may be replaced.