Syria called on the Arab nations yesterday to throw their support behind Iran in its confrontation with the United States and suggested that the Arab League summit meeting take up the issue when it convenes next week in Tunis.

Syrian Foreign Minister Abdel Halim Khaddam issued the call the day after the Arab League's foreign ministers rejected a demand by Libya to take up the U.S. freeze of Iranian assets in American banks.

"The Iranian revolution gave appreciable help to the Palestinian cause and it is normal that it should be backed by the Arabs," Khaddam said.

The foreign ministers agreed Thursday to leave it up to the summit participants to decide whether to exaimine the Libyan demands when they convene Tuesday. Libya and Iran resumed relations that were suspended nine months ago over disappearance of a Shiite leader.

The Palestine Liberation Organiation's official WAFA news agency said yesterday that "the Palestinian revolution, which stands in the same trench with the Iranian revolution . . . announces its firm stand with the Iranian masses in confronting the conspiracies being conducted by U.S. imperialism."

A spokesman for the PLO, which has acted as a go-between in efforts to ease conditions for the hostages being held at the American embassy in Tehran, refused to say whether the statement also meant support of the embassy seige.

Meanwhile, about 50 Iranian students marched to the U.S. embassy in Vienna to protest against "American imperialism" and in Munich, more than 200 American students rallied in front of the U.S. consulate to show support for President Carter's efforts to win the hostages' freedom.