UNITED NATIONS, OCT. 24 -- The United States joined in a unanimous Security Council resolution tonight that "deplores the refusal of the Israeli government" to accept a U.N. mission investigating the Oct. 8 killing of as many as 21 Palestinians in Jerusalem.

The U.S. action, its second condemnation of Israel in less than two weeks, came after President Bush sent a letter to Israeli Prime Minister Yitzhak Shamir Tuesday appealing to him to accept the U.N. mission. Shamir rejected the appeal, Israeli television reported today, and the United States then decided to support the resolution passed tonight.

This outcome seems certain to exacerbate tensions with the Jewish state that have been building since Israeli police fired on Palestinians during protests in which rocks were thrown at Jews praying at the Western Wall below Jerusalem's Temple Mount. As many as 21 Palestinians were killed in that encounter, and two others were shot dead when rioting spread to the West Bank.

Tonight's resolution urged Israel "to reconsider its decision . . . and permit the mission of the secretary general to proceed."

The United States endorsed the resolution after having won a 24-hour delay during which it sought Israeli compliance and, failing to obtain it, negotiated to tone down some of the language.

Israel contends that permitting the U.N. mission to conduct an investigation would breach its claim to sovereignty over the entire city of Jerusalem. Israeli sources asserted that the 15-member Security Council, in pursuing the matter, is singling the Jewish state out for one-sided criticism. They argued that Israel is America's oldest and most dependable ally in the Middle East and thus should have the protection of a U.S. veto.

The United States voted for an Oct. 12 council resolution condemning Israel for using excessive force and encouraging Secretary General Javier Perez de Cuellar to send an investigative team to Jerusalem. Although the United States blocked harsher condemnation, Shamir's government and its supporters in this country charged that the Bush administration was trying to appease the coalition of Arab states working with the United States to oppose Iraq's occupation of Kuwait.

Secretary of State James A. Baker III has responded that the United States voted to censure Israel as "a matter of principle," and he added that the U.S. position would have been the same even if the United States was not embroiled in the confrontation with Iraq.

Sources familiar with Bush's message, which was delivered to Shamir by U.S. Ambassador William Brown, said it commended Israel for protecting Moslem religious shrines on the Temple Mount and elsewhere in East Jerusalem. But, the sources added, the bottom line of Bush's message was to stress the U.S. view that Israel should seek a way to accommodate the U.N. mission so the Security Council could put the Jerusalem issue behind it and turn its attention back to the Persian Gulf crisis.

Israeli Ambassador Johanan Bein portrayed the vote as a victory for Iraqi President Saddam Hussein because the issue had diverted attention from the "mutilation" of Kuwait. The Palestine Liberation Organization "has served Saddam Hussein well by stealing the show," Bein said.

Bein, asked later by reporters if he felt betrayed by the United States, said, "No, we don't feel betrayed. The U.S. and others have done something wrong . . . . We've seen this film before, the double standard. The moral authority, if you listen to the speeches, are Cuba and Yemen, and we remember the atrocities there."

Sponsorship of the resolution, numbered 673, came from many nonaligned nations, including Yemen.

Other diplomats portrayed the resolution as helping to preserve the unanimity of the international coalition against Iraq. A French diplomat who asked that his name not be used said a U.S. failure to back the resolution could have led to complications relating to the Persian Gulf crisis.

Adoption of the resolution clears the way for the council to concentrate on a draft resolution affirming Iraq's liability to compensate for any loss, damage or injury as a result of its invasion of Kuwait. It invites states to collect all relevant information, including that relating to human rights abuses.

Staff writer John M. Goshko, in Washington, contributed to this story.