A delegation of 400 U.S. businessmen today ended three days of meetings with Soviet trade officials on an optimistic note.

U.S. businessman Dwayne Andreas, co-chairman of the delegation, told a news conference the ninth annual meeting of the U.S.-U.S.S.R. Trade and Economic Council had benefited from the "friendly breezes flowing from the direction of Geneva."

Andreas' Soviet counterpart, Deputy Trade Minister Vladimir Sushkov, said the meetings had been succesful in increasing Soviet confidence in American trading partners.

Both the Soviets and the American contingents have gone out of their way throughout the meetings to put a positive spin on the prospects for renewed trade between the two nations. But when the meetings ended today, the major result was more political than economic, according to several businessmen in the U.S. delegation.

Andreas said there was no report showing the results of the hundreds of private business negotiations that went on here this week. However, the Soviet news agency Tass, which has devoted considerable attention to the meetings, reported the signing of several contracts -- including the joint construction of chemical and petrochemical complexes and the purchase of medical equipment and research instruments.

Top Soviet officials, including Soviet leader Mikhail Gorbachev, opened their doors to the Americans this week as the U.S. delegation hoped to bring trade with the U.S.S.R. back to detente-era levels.

Since the late 1970s, U.S.-Soviet trade has fallen sharply, particularly after the grain embargo that followed the 1979 Russian invasion of Afghanistan. Last year, U.S.- Soviet trade rose to $3.2 billion. The increase was entirely because of huge grain sales, however, while manufactured goods still showed a decline.

The Soviet approach to the U.S. businessmen this week, in both public meetings and private conversations, has alternated between two themes -- one seeking practical results from the recent Geneva summit meeting between Gorbachev and President Reagan, and the other pressing for the elimination of "political obstacles" erected by the United States.

Those obstacles, including the withholding of "most favored nation" status on tariffs, restrictions on high-technology exports and a perceived threat of future embargoes, were listed Tuesday by Gorbachev in a candid and forceful speech on the outlook for U.S.-Soviet trade.

Today, Sushkov skirted the issue of the obstacles, and said that U.S. businesses are now negotiating for large-scale projects. "We hope results will follow," he said.

Oil exploration, an area of considerable interest to the Soviets, could be the source of major cooperative projects, council officials said.

Tass Tuesday reported an agreement with MacDermott International for joint development of ice-resistant platforms, marine pipelines and a study of oil transportation problems. The new contract suggests Soviet intentions to develop offshore drilling in the Barents Sea, an arctic area already identified as a potentially rich oil field.

At today's press conference, Andreas listed joint U.S.-Soviet oil exploration as a likely area for expansion. "We are optimistic something will develop along that line," he said. Agribusiness, chemicals and computer technology were other fields cited as areas for more trade.

For many of the businessmen here, the prospect of improved political climate spelled out the possibility of better trade.

Varian Associates, a $1 billion California-based company that has sold research and medical equipment to the Soviet Union since 1967, saw its sales go from a high of $5 million in the mid 1970s to zero in 1982 when their product came under tightened restrictions.

Those restrictions were lifted partially this year, and now Varian has built its Soviet trade back up to about $300,000, fighting for its place in a field crowded with Japanese and European competitors.

This week, four Varian representatives were in town to sign a new agreement with cautious hopes for restoring their place in a highly competitive market.

"The atmosphere is better, no question, but most of us have been in the business long enough to know it takes time," said Martin E. Packard, assistant to Varian's executive vice president.