JERUSALEM, JUNE 20 -- A plan to build a huge U.S. radio relay station in Israel's Negev Desert has been thrown into limbo by the decision of an Israeli planning commission to order a two-year study of its potential impact on migrating birds, U.S. and Israeli officials said today.

The vote Tuesday by the National Council for Building and Planning came after months of debate here and in the United States over the $290 million project, which was designed to improve broadcasting to the Soviet Union and Central Asia by the Voice of America, Radio Liberty and Radio Free Europe.

Critics said the station, which would include a field of antennas as tall as 70-story buildings, was unnecessary because of the changed political situation in the former Soviet Bloc and would harm the environment.

The unexpected decision embarrassed the government of Prime Minister Yitzhak Shamir at a time when it is struggling to patch frayed relations with the United States. The government, which had vowed to carry though the project despite opposition here, said today it was studying ways of reversing the commission's decision.

U.S. officials said that if the two-year delay is confirmed, the huge facility would probably not be built. "I believe it would be difficult because of the increased cost," said Walter Ireland, the liaison officer here for the U.S. Board of International Broadcasting, which was to operate the station. "This came as a surprise to us and it's certainly very disappointing."

Ireland said the United States already has invested $40 million in the project, including $16 million advanced to the Israeli government at the time it was agreed, in 1987. The money was to be used for planning and development projects in the area of the station, which was intended for a large tract of desert in southeastern Israel, near the border with Jordan.

Construction has not begun, but extensive work has been done to divert a highway around the site.

The planning commission's decision was a victory for an alliance of Israeli environmentalists, farmers and military commanders who opposed the project because of its potential impact on human health, bird migration, and the electronics of military aircraft in the Arava Valley. The groups have been campaigning against the project since early this year and enlisted the support of U.S. groups such as the Audubon Society.

The Israeli Society for the Protection of Nature convinced the planning commission that a detailed study must be made of the impact of the antennas' radiation on the millions of birds that semi-annually move through the area, the major migratory route between Africa and Europe and Asia.

Although U.S. officials said there was no evidence that other VOA transmitters had affected birds, Joseph Shadur, a spokesman for the Israeli society said "there hasn't been a single ornithologist who has supported VOA on this." The VOA, he said, "were warned at the beginning that this study was necessary, but they refused."

The decision put Shamir's government in an awkward position because of its commitment, reaffirmed in February, to carry out the project. "There is a decision to go ahead with the project and the government plans to go ahead with it," said Avi Pazner, a senior adviser to Shamir. "We have to study the situation and see if there are legal obstacles."

The U.S. Embassy said today that "the issue of possible damage to migrating birds from short-wave transmitters has been well studied," and "the reasons for implementing the agreement signed by our two nations in 1987 remain valid." It added, "Events in Eastern Europe and elsewhere have underscored the major role international radio can play in fostering democracy."

Some critics here and in the United States called the radio project anachronistic following the breakdown of Soviet control over Eastern Europe and the ending of the jamming of U.S. radio broadcasts. The Israeli station had been conceived in part as a way of outflanking Soviet jamming stations blocking signals by U.S. transmitters in Europe.