President Carter plans to send Secretary of State Cyrus R. Vance to meet with Soviet Foreign Minister Andrei A. Gromyko in Europe in late April, as a possible prelude to a Carter summit conference with Soviet leader Leonid I. Brezhnev.

News of the planned Vance-Gromyko meeting, probably in Geneva, first came yesterday from officials traveling with the president in Brazil.

The disclosure came two days after the Kremlin leadership asserted, through the Soviet newspaper Pravda on Tuesday, that the time is approaching "for crucial decisions in Soviet-American relations."

The article said the Carter administration was displaying "ambivalence" and "vacillation" in concluding the nuclear strategic arms limitation talks (SALT).

By making public the proposed Vance-Gromyko meeting, centered on the prolonged nuclear negotiations, the Carter administration evidently sought to demonstrate that it is not foot-dragging on SALT.

In addition, the State Department Wednesday labeled the Soviet analysis and critique of U.S. policy a "serious, thoughtful commentary" that deserves serious study.

The proposal for Vance and Gromyko to meet, administration sources said, was made before the recent Kremlin review of U.S.-Soviet policy that produced the questioning article in Pravda about the Carter administration's intentions.

Vance discussed the idea for a Gromyko meeting with Soviet Ambassador Anatolly F. Dobrynin before Dobrynin left Washington for Moscow on March 17, reportedly "loaded down" with position papers on U.S. policy. Dobrynin indicated that the Soviet Union was receptive to the idea of a Vance-Gromyko meeting, but no date has been agreed to.

Another report on the plus side of U.S.-Soviet relations yesterday was a disclosure that the Soviet Union has responded affirmatively to the Carter administration's call for negotiations to ban the use of hunter-like space satellites.

With the plan for a Vance-Gromyko conference under way, it now becomes doubly clear, in retrospect, why the Soviet Union was extra puzzled about the Carter administration's intentions on the day Dobrynin left Washington.

It was on that day that President Carter delivered a stern speech on U.S. defense and American-Soviet policy at Wake Forest University. In it, Carter said the United States will spend whatever is required on defense to "guarantee our security," and he warned of "an ominous inclination" by the Soviet Union to project its growing power around the globe, notably in the Horn of Africa.

The Pravda article on Tuesday by Soviet spedialist on American affairs Georgi A. Arbatov, pointedly asked if this represented a shift in American policy, and an attempt "to obtain military superiority . . . ?" U.S. officials have denied that. The Arbatov article signified that the Kremlin leadership was leaving the issues open.

A Vance-Gromyko meeting is expected to determine if some of the remaining barriers to a new nuclear arms control pact can be resolved.

This late-April meeting is expected to be followed by another meeting, or series of meetins, between Vance and Gromyko in this country starting in late May, when a special session of the United Nations on disarmament begins in New York.

There has been some Soviet probing at lower levels about the possibility that Brezhnev might lead the Soviet delegation to New York, opening the way for Carter-Brezhnev meeting. Many diplomats think it more likely, however, that if Vance and Gromyko make enough progress to justify a Carter-Brezhnev meeting, that meeting would be in Europe at a later date - unless it is a summit conference to confirm a virtually complete SALT accord. Carter said he is prepared to meet Brezhnev for either purpose.

From Moscow it was reported yesterday that Yugoslavian President Tito urged Brezhnev in a letter to consider action to avoid a deterioration in relations with United States.

Tito in Washington earlier this month joined President Carter in a call for settling the conflict in the Horn of Africa between Ethiopia (supported by Cuban troops and Soviet military advisers) and Somalia.

In the letter delivered to Brezhnev this week by visiting Yugoslav Foreign Minister Milos Minic, Reuter news agency reported, Tito expressed concern that attitudes between Moscow and Washington were becoming frozen. Tito is known to favor an early Carter-Brezhnev meeting.