Czechoslovakia agreed yesterday to accept U.S. terms for compensation claims for American property seized by Communist authorities, apparently clearing the way for the return to Prague of 18 tons of gold held by the Allies since the end of World War II and now worth $250 million.

Negotiators for the two governments initialed an agreement in Prague providing for an $81.5 million Czechoslovak settlement of the U.S. claims, four times the amount Czechoslovakia offered to pay in a 1974 agreement that was rejected by Congress, according to sources here.

The agreement, which would end a decades-old dispute between the two countries, is contingent on U.S. congressional approval and also on the successful outcome of similar British negotiations with Czechoslovakia.

U.S. officials, however, were optimistic about getting congressional approval and said Britain, which is to begin new negotiations with Prague next week, has "made a lot of progress" toward its agreement.

Sen. Daniel Patrick Moynihan (D-N.Y.), a leader of congressional efforts to pressure Prague into a favorable settlement, said he was "very pleased" with the agreement and hoped that "we will soon be able to implement it and provide meaningful compensation to those thousands of Americans whose property was expropriated so long ago."

Moynihan is the chief sponsor of a bill that would allow the United States to sell the Czechoslovak gold and use interest from the proceeds to compensate the claimants. The bill, which has been reported favorably by the Senate Finance Committee, "will still be pushed if the agreement falls through," a Senate source said, but he added that yesterday's agreement appeared to meet the demands of the bill's supporters.

A U.S. official in Washington said the agreement signaled no particular improvement in the long-chilly relations between the two governments but removed a major obstacle. "Our motivation was getting money for aging claimants," he said.

Senate rejections of negotiated agreements in 1964 and 1974 were followed by chills in relations between the two countries, including U.S. denial of most-favored-nation tariff treatment for Czechoslovakia and a slowdown in trade and cultural exchanges.

The gold was part of a vast store seized by the Nazis from Czechoslovakia and other countries in the late 1930s and early 1940s. After World War II the Allies captured it and a tripartite commission of the United States, Britain and France was formed to handle its return.

The return was complicated when communist governments gained control in the countries that formerly owned the gold and confiscated property, including homes and factories, owned by U.S. citizens. Over the years, agreements were reached with Hungary, Romania and other countries, allowing return of the gold for settlements in the range of 40 on the dollar.

The $81.5 million settlement agreed on yesterday by Czechoslovakia amounts to about 77 on the dollar for the $105 million in outstanding claims and interest.

Congressional sources said Prague had offered a $64.1 million settlement last summer, after negotiations had been reopened for the first time since 1975, but the United States, under congressional pressure, insisted on more.

While Czechoslovakia increased its offers, however, the value of its gold appreciated even more. The 8.2 tons held in the United States and the 10 tons held in Britain are now worth $250 million, about three times the value in 1974.

After rejecting the 1974 agreement, Congress attached an amendment to the Foreign Trade Act of that year denying Czechoslovakia the gold as well as most-favored-nation trade status and Export-Import Bank credits unless it agreed to fully pay the U.S. claims.

State Department officials said the new agreement will probably be submitted to Congress in about two weeks. The delay reportedly is to allow time for Britain and Czechoslovakia to reach a similar agreement.