NEW YORK--About 50,000 people rallied yesterday at Dag Hamarskjold Plaza across from the United Nations to protest the U.N. General Assembly's invitation to the Palestine Liberation Organization to join the U.N. debate on the Middle East.

The demonstration was the largest political protest in New York City history, a Police Department spokesman said afterwards. It was sponsored by several national Jewish organizations and was endorsed by a number of major labor unions, including the New York AFL-CIO.

Eban, Dayan, Jackson

Former Israeli Foreign Minister Abba Eban, former Israeli Defense Minister Moshe Dayan and Sen. Henry Jackson (D-Wash.) were among the speakers at the rally.

"It is one thing to confess impotence before the gun of the assassin, but it is quite another to grant him recognition and obsequious deference," Eban said. "Israel will not die and will not be swallowed up."

Dayan said, "The future of the state of Israel and of our people will not be decided by the PLO. We shall determine our own future."

Special security precautions were in effect at the U.N. throughout the day and the building was closed to visitors.

The demonstration was largely orderly, although police made 11 arrests, charging ten people with disorderly conduct and one with possession of a dangerous weapon.

Many protestors carried signs proclaiming "PLO Equals Murder," and several held coffins aloft, each bearing the name of a city in which a PLO terrorist action took place.

Numerous political figures were present at the rally, including Rep. Hugh L. Carey (D-N.Y.), Democratic candidate for governor of New York, and senatorial candidates Ramsey Clark and Jacob K. Javits.

"The PLO should be arraigned before an international court for crimes against humanity," said Clark, who has been accused by Javits of advocating the establishment of a Palestinian state.

About five blocks away from the protest, 12 supporters of the PLO stages a counter-demonstration to welcome the PLO delegates to New York.

M. T. Mehdi, head of a the American-Arab Action Committee, a New-York-based PLO support-organization, told the demonstrators. "We are opposed to the existence of a Jewish state in Palestine, just as we are opposed to any non-secular state in that area."

At one point, several people from the larger demonstration charged the pro-PLO group, but were turned back by police.

The U.N. debate on the Palestinian question, originally scheduled to begin yesterday, last week was postponed until November 13. The postponement was apparently not connected with yesterday's rally.

About 20 Harvard students organized by Harvard-Radcliffe Hillel attended the demonstration