Soviet Ambassador Anatoliy F. Dobrynin met with top-ranking U.S. officials yesterday amid increasing signs that the Carter aministration shortly will ask Congress to repeal or waive restrictions on tariff benefits and trade credits to Moscow.

An official statement on Dobrynin's meeting with Secretary of State Cyrus R. Vance and Treasury Secretary W. Michael Blumenthal said only that it concerned U.S. Soviet economic relations.

However, reliable sources reported that the purpose was to explore the possibilities of changing or circumventing the Jackson-Vanik amendment that ties the granting of most favored nation trade status for the Soviet Union to relaxation of Soviet emigration policy for Jews.

The sources said that, while no decisions have been made, Vance and Blumenthal have been actively discussing ways to get the amendment's restrictions eased. Yesterday's meeting, they added, was partly to sound out the chances for Soviet cooperation in any approach that might be made to Congress.

According to the sources, the issue is getting priority attention because it bears directly on the administration's efforts to maintain the momentum of improving relations with both communist superpowers, the Soviet Union and China.

The administration is anxious to exploit its opening of relations with China by moving ahead with trade agreements that could include most favored nation status. But, giving such status to Peking while continuing to deny it to Moscow could raise new resentments and suspicions in the Soviet Union about alleged U.S. efforts to play the two countries off against each other.

The amendment sponsored by Sen. Henry M. Jackson (D-Wash.) and Rep. Charles A. Vanik (D-Ohio), has been a chronic irritant in U.S.-Soviet relations since its adoption in 1974 as a means of trying to pressure Moscow into allowing greater Jewish emigration to Israel and elsewhere.

Passage of Jackson-Vanik, plus adoption of a limit on Export-Import Bank credits to the Soviet Union of $300 million led Moscow to repudiate a previously negotiated Soviet-American trade agreement. Since then, the amendment has come to symbolize the superpowers' failure to make much of mutual practical value out of detente.

Until recently, the administration was understood to be leery of trying to change the amendment until its strategic arms limitation treaty (SALT) with Moscow has been acheived and ratified by the Senate. That strategy was designed not to antagonize Jackson and other Senate supporters of the amendment whose votes are being courted by the adminstration for SALT.

According to the sources, though, the administration now is weighing a change in that strategy because of several factors that may have improved the chances for successfully getting changes in Jackson-Vanik through Congress.

Chief among them has been a big surge in the rate of Jewish emigration from the Soviet Union. More than 31,000 Jews were allowed to leave last year, and emigration so far this year has been averaging 4,000 a month. In the four years before 1978, emigrations averaged about 16,000 annually.

Recognition of China and congressional eagerness to move forward on trade with China are other significant factors. Although Jackson-Vanik's restrictions apply to China as well as certain other socialist states, the recent Chinese record on relaxing emigration controls is considered by many observers as bringing Peking into compliance with the amendment's requirements.

These factors, together with Soviet cooperation in the SALT negotiations and other gestures like yesterday's prisoner exchange, appear to have caused many members of Congress to take a new look at the issue. Even Vanik, who recently visited Moscow, has said the time may be ripe for a change. However Jackson still remains opposed to easing the amendment for Moscow's benefit.

If the administration does decide to move, the sources said, it almost certainly will seek to do so under the amendment's "waiver" provisions. These empower the president to declare that the Soviets have complied with the amendment's emigration requirements and grant special trade status unless Congress objects.

The danger there, according o the sources, involves unclear legal questions about whether the president's declaraion must be backed by some kind of official documentation or pledge from the Soviets, who have consistently denounced Jackson-Vanik as an interference in their internal affairs.

That, the sources continued, led to yesterday's meeting as part of an attempt to determine whether Soviet leaders will cooperate in efforts to assure Congress of their compliance and not say or do anything to undermine the administration's drive for a waiver.

The meeting was the first in many weeks between Vance and Dobrynin which did not center on the nearly completed SALT. Informed sources said U.S. proposals for settling some of the few unresolved issues were given to Dobrynin Wednesday, with a reply expected soon from the Soviet side.

Among the remaining questions is a U.S. proposal to deal with the Soviet capability, demonstrated in a missile test last Dec. 26, to launch more than 10 reentry vehicles, or warheads, from an SS18 land-based intercontinental missile. Ten independently targetable warheads will be the limit under SALT II.

While the Soviets did not actually launch more than 10 warheads last December, their apparent capability to do so caused concern among some U.S. officials. The U.S. proposal on this issue is reported to be an attempt to distinguish in clearly verifiable fashion between the allowed maximum of 10 warheads on the one hand, and additional dummy warheads or chaff on the other hand.