With a congressional showdown over the Turkish arms embargo rapidly approaching, the Turks yesterday made a conciliatory gesture by offering to accept a limited United Nations role in one of the principal disputed areas of Cyprus.

The Turks said their proposal was designed to revive the long dormant intercommunal talks. A senior Carter administration official said the United States was prepared to "serve as intermediary" in bringing Greek and Turkish Cypriots to the negotiating table.

Although the text of the Turkish proposal was deliberately ambiguous, it did envision a U.N. role in an interim administration of Varosha, the Greek part of the city of Famagusta, and the return of as many as 35,000 Greek Cypriot refugees to their Varosha homes once the talks get under way.

Greek Cypriot sources here immediately pointed out the ambiguity of the Turkish proposals, the absence of a defined area of resettlement and the Turks' obvious intention to create a favorable impression here before the vote next week in the Senate on the proposed lifting of the arms embargo against Turkey.

The proposals left open to question the precise naure of an "interim administration under the aegis of the United Nations" as well as the claim that 35,000 Greek refugees would be affected.

Senior U.S. officials, who have worked with the Turks on the formulation of the proposals over the past several weeks, insisted that "our intepretation based on our discussions with the Turks indicated that the U.N. would take the primary role in administering the area."

But they said "there is no question that the Turks want to demonstrate their flexibility to the U.S. Congress" and thus help influence the votes next week on lifting the arms embargo.

Varosha, once the principal tourist center of a thriving Cyprus tourist industry, has been completely empty since its Greek inhabitants fled before the invading Turkish forces following Turkey's occupation of two-thirds of Cyrus in the summer of 1974.

As a result of the Turkish action, which was in violation of U.S. arms aid law, Congress imposed the embargo on arms shipments to Turkey in 1974. The restriction was eased a year later allowing the president to sell the Turks up to $175 million in arms annually so that they could meet their NATO commitments.

The Turkish proposals, made in the form of an open message by Turkish Cypriot leader Rauf Denktash, includes the following points:

An Interim administration to be promptly established in Varosha "without any prejudice to the existing or the final political status of the area."

The administration to be established "under the aegis of the United Nations" simultaneously with the resumption of the intercommunal talks.

Its functions would include the supervision of essential municipal services and police functions.

The resettlement by stages to begin "as soon as feasible with the resumption" of talks.

Given the nearly complete Turkish intransigence on the Cyprus question during the past three years, State Department officials said yesterday's limited move was encouraging. President Carter and Deputy Secretary of State Warren Christopher have briefed several congressional leaders in an effort to win more votes for the administration's bid to repeal the arms ban against Turkey.

There were no indications yesterday whether the Turkish proposals offered substantial concessions for several key supporters of the continued ban to change their positions. House Speaker Thomas O'Neill, who supported the ban, said, "Well, maybe the concrete is loosening."

The Cyprus government will annouce its response to the proposals today, according to Cypriot diplomats. In the past year, President Spyros Kyprianou had insisted on the withdrawal of foreign troops and the return of more than 200,000 Greek Cypriot refugees to their homes as pre-condition for any Cyprus settlement.

In a speech last night marking the fourth anniversary of the Turkish invasion, Kyprianou appeared to reject the Turkish proposals.

"If Denktash wants a solution," Kyprianou said, "let him present a plan in which Varosha would be left in the hands of the Cyprus government. Let him present a plan for a real federation with freedom of movement, settlement and property rights and the withdrawal of foreign troops."