Socialist leader Andreas Papandreou, whose party was swept into power with an overwhelming victory in parliamentary elections yesterday, plans to concentrate on domestic and economic issues immediately, delaying major moves in foreign policy.

Papandreou, who is expected to name Greece's first socialist Cabinet on Wednesday, said last night that the immediate goals of his government will be the revitalization of the economy and decentralization of public administration.

His Panhellenic Socialist Movement (Pasok) campaigned on a platform advocating Greek withdrawal from the North Atlantic Treaty Organization, putting the issue of European Community to a referendum and shutting down U.S. military bases in Greece. Aides indicated today, however, that there will be no immediate moves in these areas and that discussions on the U.S. bases will not resume before March.

Secretary of Defense Caspar W. Weinberger warned that Greek withdrawal from NATO could weaken the alliance but said he saw little likelihood of an immediate move. The Soviet press said the socialist victory showed popular Greek support for withdrawal.

Virtually complete election results indicated that Papandreou's party won 48 percent of the vote and 174 seats in the 300-seat Parliament. The New Democracy party, under Prime Minister George Rallis, which had ruled for the past seven years, got 36 percent of the vote and 113 seats. The Communist Party got 11 percent of the vote and 13 seats.

The new socialist administration will be trying to combat an annual inflation rate of more than 25 percent and a balance of payments deficit that might reach $2.5 billion this year.

Papandreou, who describes Pasok's brand of socialism as "virtually identical" with that of France's Socialist president, Francois Mitterrand, and who has watched closely during the past months the changes made in France, intends to follow the French Socialists' efforts on decentralization, a stronger government grip on the economy and reflation through increasing buying power.

While economic and social issues were clearly the primary concerns of Greek voters, the West will be watching closely to see how faithfully Papandreou will adhere to his foreign policy goals.

Papandreou, who lived in the United States for 20 years and became a U.S. citizen -- later renouncing the citizenship when he returned to politics here -- said in the late days of the campaign that his understanding of Americans could help him secure an agreement beneficial to Greece if it decided to allow U.S. bases to remain.

While he has said he would ultimately like to see the bases go, he has emphasized that he will discuss with the United States the use and control of the bases and the economic and military aid Greece might receive in exchange for their continued operation here.

Negotiations on the U.S. bases were suspended before the elections by the outgoing government. Papandreou believes that Pasok will be a more consistent and pragmatic bargaining partner on the issue.

"I have spent over 20 years of my life in the U.S. and I am very familiar with the patterns of American behavior and thought," Papandreou, who has taught at the universities of Minnesota, Northwestern and California at Berkeley, said in a press conference in Salonika 10 days ago.

"I can talk their language much more clearly than the right. The Americans must know what our aims are."

In a telephone interview with John Cooley of ABC, Papandreou said, on the issue of U.S. bases, "What we look forward to is the opening of negotiations . . . . Not immediately, for there are many more immediate, pressing issues for us."

Papandreou has said he regards a "French-style" relationship with NATO as ideal. France, in 1966, withdrew from the integrated military command of NATO and participates only in selected NATO activities. Greece withdrew from the military wing of NATO in 1974 at the time of the Turkish invasion of Cyprus and rejoined it last year.

In a recent interview, Papandreou indicated that he would be willing to stay with NATO if Greece could be guaranteed the military equipment necessary to defend its eastern borders against a possible Turkish threat.

Papandreou told Cooley: "We are the only member of the Atlantic Alliance that faces a danger and a threat from another member of the alliance, namely Turkey. And it is a matter of the first order that NATO, an alliance to which we belong at this point, is not the best to guarantee our frontiers in the Aegean. This is a unique problem. It is an alliance which really doesn't guarantee your territorial integrity."

A further major irritant for Greece's relations with NATO is the issue of Cyprus, whose President Spyros Kyprianou is expected in Athens this week for consultations over the latest proposals by U.N. Secretary General Kurt Waldheim for a settlement on Cyprus.

Papandreou has indicated that he will take a tough stand against NATO ally Turkey on the issues of Cyprus and territorial disputes covering the airspace and continental shelf of the Adriatic Sea.

"The intercommunal negotiations on the Cyprus issue are unacceptable while Turkish troops remain on the island," Papandreou said in Athens Thursday. "We want full demilitarization of the island and we will back the Cypriot government actively in its efforts for a just solution."

In his interview with Cooley, Papandreou also made the following points:

* "Pasok has been represented repeatedly in the foreign press as an anti-European and anti-Western party. This has been just bad publicity because Pasok is very much of a European party. We have tremendous bonds with all the socialist and social democratic and labor movements of Western Europe" including those in France, Britain, Norway, Denmark, West Germany, Italy and Spain.

* "Greece is a highly centralized country. We have a very powerful central government, a huge bureaucracy. Our objective is to decentralize, to give more powers to local government, and at the same time take such measures as are necessary to turn our various public enterprises from budgetary deficit operations to successful cost-minimizing operations."

* "We have to also bring in some democratic freedoms. Television and radio have been up to now a monopoly of the government. We shall do away with this monopoly we shall open television and the radio, all the mass media of communications, to all parties and social forces."

Staff reporters and news services reported the following reaction to the Greek election:

The official Soviet news agency Tass said the strong socialist showing "testifies to the growing public support of the party's demand for the withdrawal of Greece from the NATO military organization" but it warned that "right-wing forces within Greece" could put "serious obstacles" in the way of such a move.

A commentator for Novosti, a Soviet press agency, urged Papandreou to take up an earlier offer by Soviet President Leonid Brezhnev for a treaty under which Greece would bar nuclear weapons from its territory in return for Moscow's promise never to use nuclear weapons against Greece.

Washington Post staff writer George Wilson reported from Stockholm that U.S. Defense Secretary Caspar W. Weinberger said, "I think it would unquestionably weaken the NATO alliance if Greece did decide to pull out. I would hope there would be a strong enough popular move within Greece that would persuade Papandreou that would not be the case."

Weinberger added, "Sometimes there's quite a wide gap between campaign rhetoric and the realities as faced when you are actually in government."

President Reagan, in Yorktown, Va., said, "That's too bad," when a reporter called out that Greece might pull out of NATO. Asked what could be done about it, Reagan said, "I don't know. We'll have to see."

A Turkish Foreign Ministry spokesman said the Ankara government would await the program adopted by Pasok before commenting on the Socialists' victory. "It's a bit early for an evaluation. We'll find out how things work in practice," he said.