The Reagan administration has taken a first step toward aiding the hard-pressed government of Poland by deciding to let that country defer repayment of more than $80 million owed to the United States, State Department sources said yesterday.

The U.S. contribution to the easing of Poland's severe debt problem is to be made known officially in Paris meetings, beginning today, of representatives of Poland's western creditors.

A senior U.S. official familiar with administration thinking portrayed the current debt deferral, which involves Commodity Credit Corp. funds, as "bridging assistance" for the Warsaw government, which faces an economic crisis.

The Reagan administration's decision, while limited in scope and economic scale, is one of the first indications of how it will deal with the thorny problems of U.S. relations with Eastern European nations on the Soviet periphery. It was taken in the light of strong and continuing western concern about a possible Soviet invasion of Poland, which would bring on an East-West crisi of major dimensions.

A longer term and more imposing plan of assistance to Poland is under study within the administration, sources said. Such a program would be considerably more complicated in its political and economic ramifications, both here and abroad.

A major aid program is likely to require much greater confidence than currently exists that the Polish regime will survive the combination of internal instability and Soviet external pressure. It probably also would require explicit commitments by the Warsaw government to implement economics reforms so that the aid would not be wasted.

Moreover, a major aid program to Poland would have to be reconciled with the Reagan administration's high priority budget cutting program.

In the past months of the Carter administration, Poland asked the United States for $3 billion in "emergency assistance," involving debt deferrals, new loans and other types of aid. After a policy dispute in the postelection period, the outgoing administration decided to take no action, leaving the Polish aid question to its successor.

The Reagan team's decision on the immediate debt deferral question was made easier by the fact that more than 15 countries are to be represented in this week's Paris meetings, organized by the French government to consider handling of the debts that come due between now and June 30. With other nations present expected to make pledges that will total between $600 million and $700 million, failure of the United States to contribute would have sent a powerful signal of international negativism.

The Soviet Union, in a move that appears to have been timed to facilitate western assistance at the Paris meeting, agreed last week to a four-year moratorium on the repayment of its debts by the Warsaw regime. This decision was also seen as a sign of Soviet goodwill toward the new government of Gen. Wojciech Jaruzelski, who came to power as prime minister two weeks ago in a last-ditch effort to stabilize the political and economic situation.

Poland owes about $23 billion to western creditors, mostly European nations and banks. The U.S. share of this debt, estimated at $2.5 billion, is predominantly in government loans such as those of the CCC.

The heavy external debt calls for Poland to pay more than $10 billion per year in principal and interest, vast sums that are unavailable to the regime. Failure to give Poland relief from these payments, in the western view, would add new fuel to the crisis there and could even bring about a Polish default on its international obligations, with large-scale consequences both for that country and the global financial system.