Despite the veto, U.N. Security Council members were expected to discuss a separate resolution that would briefly extend the Bosnian mandate. This would give more time to try to resolve the dispute that pits the United States against almost all 14 other members of the powerful council.

If no agreement is reached, the 1,500-strong U.N. police training mission in Bosnia would end at midnight Sunday.

The United States is demanding that American peacekeepers be exempt from arrest and prosecution by the court, which comes into existence on Monday. The United States has rejected all compromises that don't grant blanket immunity.

The United States says immunity is needed to prevent American troops and citizens from frivolous and political motivated prosecutions. Opponents say there are enough safeguards to prevent such abuse.

The 14 other council members -- including close U.S. allies Britain and France -- support the new court and argue that a U.S. exemption would undermine the tribunal and international law.

In Sunday's vote, 13 countries voted in favor of extending the mandate for Bosnia's U.N. police training mission for six months and the authorization for the 17,000-strong, NATO-led force in the country for a year. Bulgaria, a sponsor of the resolution, abstained to highlight the absence of council unity but said it still supports the court.

U.S. Ambassador John Negroponte said the United States voted against the resolution "with great reluctance" but will not ask Americans in U.N. peacekeeping missions "to accept the additional risk of political prosecution before a court whose jurisdiction the government of the United States does not accept."

"The United States will remain a special target," he said, "and we cannot have our decisions second-guessed."

Supporters of the court expressed dismay at the U.S. action, which could affect the 14 other U.N. peacekeeping missions as their mandates come up for renewal in the Security Council.

"History, I believe, will record the actions of the U.S. administration of President George W. Bush to wreck U.N. peacekeeping and the International Criminal Court as one of the most shameful lows in global U.S. leadership," said William Pace, head of the International Coalition for a Criminal Court, a coalition of more than 1,000 organizations supporting the tribunal.

U.N. Secretary-General Kofi Annan urged the council to intensify high-level negotiations to find a solution.

"The world cannot afford a situation in which the Security Council is deeply divided on such an important issue, which may have implications for all U.N. peace operations," he declared.

A U.S. official said both Secretary of State Colin Powell and National Security Adviser Condoleezza Rice were involved in high-level discussions over the weekend on the Bosnia resolution.

The veto won't stop the world's first permanent war crimes court from coming into existence on Monday. Dutch administrators overseeing its initial months of operation are ready to register claims of genocide and wartime atrocities.

With the backing of 74 countries -- despite fierce opposition from the United States -- The Hague-based institute will have the authority to prosecute individuals -- not states -- suspected of war crimes anywhere in the world.

The International Criminal Court will not have the power to try offenses committed before July 1, 2002.

The start of the court's jurisdiction signals the beginning of "the greatest institution of peace ever created," Pace said. "All who believe in democracy and justice and the rule of law can celebrate.

"This is truly one of the greatest advances of international law since the founding of the United Nations 57 years ago."