The United States today vetoed a Security Council resolution condemning Israeli policy in southern Lebanon despite threats by Shiite Moslem militants to retaliate. Lebanon charged that the U.S. action would encourage Israeli brutality there.

Eleven countries voted for the resolution and only the United States opposed it, with Britain, Australia and Denmark abstaining. An opposing vote by any of the Security Council's five permanent members blocks adoption of a resolution.

The overwhelming vote in support of the Lebanese-sponsored text came despite an intensive U.S. lobbying effort to dissuade other council members from providing the nine-vote minimum needed to force a veto.

Washington's effort to avert the veto was motivated in large part by threats of radical Shiite groups in Lebanon that Americans there would face reprisals if the United States blocked the resolution. U.S. Ambassador Jeane J. Kirkpatrick cited the threats but said the United States would not be intimidated.

The United States vetoed a similar resolution Sept. 6, and on Sept. 20 a suicide truck-bomb attack on the American Embassy annex northeast of Beirut killed 12 persons, including two Americans.

The resolution vetoed by the United States today would have condemned "Israeli practices and measures against the civilian population in southern Lebanon . . . which are in violation of the rules and principles of international law." It would have directed a fact-finding mission to report on Israeli activities in Lebanon and it called on Israel to halt immediately its crackdown there and withdraw its forces "unconditionally."

At U.S. request, the United Nations has withdrawn 36 Americans who worked for its peace forces in the Beirut area and in southern Lebanon. U.S. officials said other unspecified precautions have been taken to avert another attack.

Four council members -- France, Thailand, Peru and Trinidad and Tobago -- said they would have preferred modifications in the draft urging all parties to refrain from the use of violence. But after Lebanon rejected last-minute amendments offered by Britain, they voted for it together with the Soviet Union, the Ukraine, China, Egypt, India, Madagascar and Burkina Faso (formerly Upper Volta).

Israeli Ambassador Benjamin Netanyahu told the council that the debate would not stop Israel from enforcing its policy or proceeding with its withdrawal. But he predicted that it would "encourage the forces of fanaticism and extremism," and said the vote for the resolution showed "a truly historic surrender to blackmail by members of the Security Council."

Kirkpatrick criticized Lebanon for refusing to negotiate a consensus text and rejecting amendments. She said the United States remains willing to join in a council statement expressing dismay at the escalating violence, urging restraint and affirming the applicability of international conventions on the protection of civilians in occupied territories.

She complained that the council debate was unfair to Israel because it reflected a double standard rather than the realities of Lebanon. "There is a cycle of violence; that fact in the world is not altered by its denial in this council," she said.

After the vote Lebanese Ambassador Rashid Fakhoury told the council, "We are in the right, and this needs no consecration through a resolution."

He said the U.S. veto "left the people of southern Lebanon the victim of Israeli crimes, encouraging Israel to proceed with its brutal policies in defiance of the international community."