A senior Soviet Embassy official yesterday described the Reagan administration's proposal for "umbrella talks" on arms control as unprecedented in U.S.-Soviet relations and said Moscow is awaiting further specifics before making a definitive response.

Among other things, the diplomat said, the Soviet side is attempting to learn at what level of government and in what city the proposed talks might be held, where the United States thinks they might lead and what issues would be considered first. The last point is of central importance to Moscow, which has given high priority to talks aimed at averting antisatellite and space weaponry while refusing to engage in negotiations on offensive nuclear missiles.

The Reagan administration, on the other hand, is eager to engage the Soviets on offensive strategic arms but reluctant to negotiate about space weapons in view of President Reagan's strong commitment to a space-based Strategic Defense Initiative.

The Soviet official spoke to reporters at a Soviet Embassy reception and asked that his name not be used. Soviet Ambassador Anatoliy F. Dobrynin, host of the reception, said in a brief speech that "there should be and are openings and possibilities for a fruitful dialogue and cooperation based on mutual interest and respect."

A senior White House official last week listed six areas for discussion under "umbrella talks": intercontinental ballistic missiles, medium-range missiles in Europe, weapons in space, chemical weapons, confidence-building measures and conventional forces in Europe. He spoke of the proposed discussions as being "across the board" but did not say how they would work.

"You introduced something new in the history of Soviet-American relations, the umbrella. What is it?" asked the Soviet diplomat in a joshing exchange with U.S. reporters. "A mackintosh raincoat we can understand, but this must be studied," said the official.

Dobrynin reportedly probed for details of the U.S. proposal during a meeting here with Secretary of State George P. Shultz on Oct. 26. Soviet Foreign Minister Andrei A. Gromyko is said to have raised similar questions on Oct. 31 in a Moscow meeting with U.S. Ambassador Arthur Hartman.

Shultz met yesterday with Reagan and his national security affairs adviser, Robert C. McFarlane, to discuss a foreign policy agenda for Reagan's second term. Officials said arms-control negotiations with the Soviet Union are at the top of the agenda.

A State Department official said the United States is likely to provide additional details of the umbrella proposal to the Soviet Union through diplomatic channels after Thanksgiving.

The White House made public a Reagan message to Soviet leaders, responding to congratulations on his reelection. "Despite our different political beliefs and perspectives on international problems, I am confident we can make progress on strengthening peace and resolving our differences through discussions and negotiations," Reagan said.

Soviet sources said they knew of nothing to substantiate reports that Shultz and Gromyko might meet in Moscow in January to inaugurate a new phase of superpower discussions. The two seemed to agree during Gromyko's late September trip to Washington that another meeting might be a good idea, said a Soviet diplomat, who added that there has been no active discussion of such a session in the present diplomatic dialogue.

Officials on both sides said the U.S.-Soviet schedule already calls for a visit here next month by the Soviet minister of agriculture, Valentin K. Mesyets, to reciprocate for a 1983 Moscow trip by U.S. Secretary of Agriculture John R. Block for the signing of a five-year grain agreement.

In another development, U.S. sources said a Soviet mission is due here in January to begin Coast Guard talks on search and rescue operations.

Earlier, it was announced that bilateral talks by experts on preventing the proliferation of nuclear weapons will begin in Moscow on Nov. 28 and that Undersecretary of Commerce Lionel H. Olmer will lead a delegation to Moscow on Jan. 8 to seek improvements in trade relations.

The Soviet Embassy reception was to mark the publication by a U.S. firm, Praeger Publishers, of a collection of writings about Soviet-American relations by President Konstantin U. Chernenko. Ron Chambers, editorial director of the publishing firm, said 2,000 hardbound copies, with red covers, are being printed in the initial press run.

In a foreward to U.S. readers, Chernenko said, "We have no alternative but to live together. This being so, it is better to live not in an atmosphere of enmity and fear, but in peace, as human beings should live, observing certain standards in our relations."

Chernenko disputed unnamed "people in your country" who say that U.S. military superiority is necessary for arms-limitation agreements.

On the contrary, Chernenko wrote, "Striving for military superiority and conducting honest, business-like talks on questions that affect the national security of the two parties are incompatible. The uncontrolled escalation of the arms race and its extension even to outer space -- this, in the final analysis, is a threat to the United States' own security."