UNITED NATIONS--Secretary-General Javier Perez de Cuellar said the United States is violating its U.N. treaty by preventing PLO chief Yasser Arafat from speaking to the General Assembly.

He warned that the U.S. decision could hamper Middle East peace efforts.

Arab diplomats, meanwhile, said they have enough votes to move the session from New York to Geneva so Arafat can address the world body on the Palestinian issue.

Perez de Cuellar, in a statement released through a spokesperson, said the decision to deny Arafat a visa to enter the country runs counter to the 1947 agreement under which the United States promises not to interfere in U.N. matters.

"The secretary-general regrets the denial of the visa application of Mr. Yasser Arafat, chairman of the Palestine Liberation Organization, by the U.S. authorities," said spokesperson Francois Giuliani last night.

"Such a decision is incompatible with the obligations of the host country under the Headquarters Agreement. If maintained, this action is likely to complicate and render more difficult the further debates on the question of Palestine and the situation in the Middle East in the current session of the General Assembly.

"This would be unfortunate at a time when, in the view of the secretary-general, the recent meeting of the Palestine National Council in Algiers provides fresh opportunities for progress towards peace in the Middle East," Giuliani said.

The Palestine National Council, a PLO parliament-in-exile, proclaimed an independent Palestinian state during its meeting in Algiers on Nov. 15.

It also implicitly recognized Israel by endorsing a U.N. resolution that guarantees all Middle East states the right to exist in peace and promised to restrict guerrilla activity.

The PLO has non-voting observer status at the United Nations and is a member of the Arab League.

Secretary of State George P. Shultz said Saturday that Arafat would not be allowed to attend this week's U.N. debate on the Palestinian issue because of evidence that Palestine Liberation Organization elements "have engaged in terrorism against Americans and others."

President Reagan told reporters in Santa Barbara, Calif., yesterday that he supported Shultz's decision. "I think the other way would have sent out the wrong signal--that we are patsies," he said.

But Jordan and Egypt agreed to spearhead the effort to reconvene the world body in Geneva, Jordan's official news agency reported.

Also, Iraq has requested a meeting at noontoday of the U.N. Committee on Relations with theHost Country to consider the U.S. move. U.N. legalauthorities also are expected to comment on theU.S. decision.

Reaction to the U.S. decision from othernations was largely negative. Israeli leaderspraised it, but Algeria, Egypt, France, Libya,Norway and Sweden were among nations whichprotested the decision. Italy summoned a U.S.Embassy official to explain the decision