President Reagan is sending a stripped-down delegation of Vice President Bush and Secretary of State George P. Shultz to Moscow today for the funeral of Soviet leader Leonid I. Brezhnev and the first American encounter with his successor, Yuri V. Andropov.

Administration officials reiterated, as Reagan said Thursday night, that the president's absence from the U.S. delegation is "a plain case of looking at schedules." He is scheduled to meet West Germany's new chancellor, Helmut Kohl, here on Monday.

Nevertheless, the Reagan decision not to go to Moscow, as Shultz and other advisers had privately urged him to do, added up to a clear signal that no overtures to ameliorate U.S.-Soviet relations will be forthcoming in the near term from the United States.

Sen. Paul E. Tsongas (D-Mass.) deplored Reagan's decision as "a lost opportunity" to make "a dramatic gesture" that "would have cost absolutely nothing."

The small U.S. delegation to the Monday funeral -- it was limited in size by Soviet decision -- indicates that the Kremlin, in turn, is making no special overture to the United States. A trip to Moscow by an American president would require a sizable entourage of staff and advisers.

The American delegation will be limited to Bush, Shultz, Arthur A. Hartman, the U.S. ambassador in Moscow, and Shultz's wife, Helena. The Soviet Union "asked that the delegation be small," White House spokesman Larry Speakes told reporters.

State Department sources said all nations have been asked to limit the size of their delegations. Bush will have to interrupt a lengthy trip to Africa to attend the funeral on Monday.

Administration reaction to the choice of Andropov as general secretary of the communist party was notably noncommittal.

It was not "too much of a surprise for anyone," President Reagan told reporters in a brief exchange as he was leaving a White House ceremony honoring youth volunteers.

"I think they made a swift transition in the interests of order," Reagan said.

When asked if he could work with Andropov, the president gave the only reply possible to such a question, "I am sure we can."

Shultz said at a breakfast meeting with Washington Post editors and reporters yesterday that there is a transition in the Soviet Union only in the "sense of a different person in charge" from the Brezhnev circle of associates, "but how much of a transition in policy remains to be seen."

Andropov's elevation to the peak of Soviet authority turns him literally overnight into one of the most powerful -- and least known -- major actors on the world scene.

His lengthy service as the head of the Soviet KGB, which is a worldwide intelligence-gathering and operational organization, and not simply a secret police agency, gives Andropov some unique advantages over all other current world leaders. Andropov for three decades has been deeply involved in international affairs to an extent unmatched not only by President Reagan, but also by British Prime Minister Margaret Thatcher, French President Francois Mitterrand and West German Chancellor Kohl.

Although Andropov is being described in seemingly great detail by western reporters and analysts, "he's had virtually no contact with western officials," a senior U.S. intelligence official said yesterday.

William G. Hyland, one of the most experienced American specialists in dealing with the Soviet leadership at its highest level, said yesterday, "I do not know anyone who actually met Andropov."

Hyland, who has held high national security posts in the Central Intelligence Agency, the State Department and the White House, was a participant in about a dozen meetings with Brezhnev and his advisers during the Nixon, Ford and Carter administrations.

"I know he [Andropov] wasn't in those meetings," Hyland said. He said he tried in vain to find Andropov at numerous receptions for Soviet officials.

Andropov has been characterized in western accounts as anything from "a closet liberal" to a debonair connoisseur of fine painting and wine, fluent in English, western-oriented and a champion of detente. Hyland said that he "would take all those descriptions with a grain of salt."

Other U.S. specialists on the Soviet Union similarly cautioned yesterday against construing Andropov as "a liberal" in western context, noting that he was the Soviet ambassador in Budapestin 1956 when the Hungarian revolution was crushed, and has directed the smothering of dissent in the Soviet Union.

It would be more accurate, one senior administration analyst said, to describe Andropov as "an activist-pragmatist" in Soviet terms.