President Carter's campaign to curb overseas arms sales has not reduced the flow of weapons to Third World countries and "there is universal skepticism" about the future of the policy, a Senate report said yesterday.

The study by the Senate Foreign Relations Committee said the unilateral effort by the United States "is under attack from both critics and supportes. It is criticized on the one hand for lack of vigorous implementation and on the other for placing the United States at a competitive disadvantage in the world's arms markets."

It added, 'Both criticisms are partially accurate."

The 20-month-old policy puts an annual ceiling on U.S. arms sales to all nations except Japan, Australia, New Zealand and NATO members.

The 1979 ceiling of $8.5 billion "may be meaningless" because of contract concellations by Iran and a one-year suspension in new arms sales for Taiwan, the study said. Because of these cutbacks, "the ceiling is instead likely to become a target."

The report said the future of the U.S. policy depends on the progress of negotiations aimed at getting the Soviet Union to agree to restrict arms sales.

Those talks were set back during negotiations in Mexico City because of U.S. refusal to discuss arms curbs in the Persian Gulf, China or Korea, according to the study.

The report said "elements" in the U.S. and Soviet military leadership "appear to question the wisdom" of "the talks appear to be accorded a relatively low priority compared with more pressing issues."

In addition, the study added, neither side has a clear idea how to broaden the talks to include other supplier nations and countries that purchase the weapons.

European suppliers compete virgorously with the Soviet Union and the United States for arms deals and depend on export sales for the survival of their arms industries, said the report, adding that "Europeans are almost unanimously skeptical about U.S. performance so far."

The two largest European arms suppliers, France and Britain, are very reluctant to join in the U.S. Soviet talks, the study added.

Between 1974 and 1977, Third World countries signed contracts for $90 billion worth of military equipment and services-about half of it from the United States.

During the same period, industrialized nations delivered $47 billion worth of arms to developing countries, with the United States accounting for 43 percent and the Soviet Union 32 percent.

"Until recently there were few signs that the executive branch was seriously implementing the president's policy," the report said.

It noted, however, that in recent months the president has rejected or delayed three controversia sales-F4Gs for Iran, F5Gs for Taiwan and F16s for South Korea.

If efforts to restrain global arms sales fail, the United States might want to abandon current policy and launch a U.S. arms export promotion policy "to make clear to Soviet and European negotiators that the United States can dominate the market," the study said.

"This would be done to convince other suppliers to take U.S. arms limitation proposals more seriously," it added.