The United States will probably vote against a proposed advisory code of ethics for the marketing of breast-feeding substitutes at the World Health Assembly in Geneva next week, government spokesmen said yesterday.

The State Department raised the possibility of an abstention, but the Department of Health and Human Services and a White House aide said that the U.S. delegation will cast a "no" vote. No other nation is expected to oppose the code.

The expected "isolation" of the United States resulting from either a no vote or a "hard abstention" could have political and foreign policy "repercussions," a State Department source told The Washington Post. He said it was a "tactical" question whether such an abstention would confer any benefits.

The draft code, while intended primarily as a barrier to commercial efforts to switch Third World women from breast-feeding to formula or other substitutes, contains no exceptions for developed nations.

The code is supported by a coalition of religious, health, and other groups and opposed by the three U.S. producers of infant formula and the Grocery Manufacturers of America.

HSS Secretary Richard S. Schweiker said it would be "hypocritical" for the United States to vote for the code because it contains provisions that, if implemented here, would violate First Amendment protections, such as those accorded commercial speech, and the antitrust laws. This view was upheld last month by the Justice Department, although it did not say that the United States could not vote for the code.

Code supporters counter by stressing non-binding code language that urges implementation with "suitable measures . . . appropriate to [each nation's] social and legislative framework."

Schweiker rejected a recommendation by one of his top health officials, Dr. John H. Bryant, that the United States cast a "yes" vote.