Dr. Fayez Sayegh, 58, senior adviser to the Foreign Ministry of Kuwait and the principal author of the 1975 United Nations resolution denouncing Zionism as a form of racism, died Tuesday in New York City after a heart attack.

Dr. Sayegh had been president of the Palestine Arab Congress and had been a member of the executive committee of the Palestine Liberation Organization (PLO) since 1965. He was head of the League of Arab States offices in Washington from 1970 to 1974. He was a member of the Palestine National Council.

In addition to his post as senior adviser to the U.N. delegation of the Kuwaiti Foreign Miinistry, he had been an adviser to the governments of Yemen and Lebanon and had served as permanent observer of the League of Arab States at the U.N.

The U.N. resolution denouncing Zionism was passed by the General Assembly on Nov. 10, 1975 by a vote of 72 to 35 with 32 abstentions and three delegations absent. It defined Zionism as a "form of racism and racial discrimination." The vote was denounced by Israel, the United States and France.

The then U.S. Ambassador to the United Nations, Daniel Patrick Moynihan, declared that the United States "does not acknowledge it, will not abide by [it], it will never acquiesce in this infamous act."

Dr. Sayegh said that the resolution he authored was in line with an earlier U.N. resolution on racial discrimination that had denounced "distinction, exclusion, restriction or preference based on national or ethnic origin." Zionism, he said, was a movement which manifests itself by "excluding some people on the basis of their being non-Jews and including others on the basis of their being Jews -- Jewishness being defined officially as an ethnic and not strictly religious definition."

Born in Syria, Dr. Sayegh was reared in Tiberias on the Sea of Galilee in what was then Palestine. He earned bachelor's and master's degrees at the American University in Beirut and a doctorate in philosophy at Georgetown University here.

In addition to his political activities, he had been a writer and lecturer. He taught courses in the social sciences and philosophy at Stanford University, at St. Anthony's College, Oxford, of which he was a fellow, at Yale University and at the American University of Beirut.

Dr. Sayegh's survivors include his wife, Ariene of Pleasantville, N.Y.