Senate Democrats today rebuffed President Bush's call for an immediate vote on his nomination of John R. Bolton to be the new U.S. ambassador to the United Nations, instead opting to keep debate open until the administration provides documents that Democratic leaders have requested.

The vote of 54 to 38 in favor of cutting off debate and sending the nomination to a floor vote fell short of the 60-vote threshold needed to invoke cloture. It was the second time that Senate Democrats had blocked an "up-or-down" confirmation vote on the Bolton nomination as demanded by Bush and Republican lawmakers.

Among those voting against the cloture motion were Sen. George Voinovich (R-Ohio) and Sen. James Jeffords (I-Vt.). Crossing the aisle to vote with the GOP in favor of cutting off debate were Democratic senators Mark Pryor of Arkansas, Ben Nelson of Nebraska and Mary Landrieu of Louisiana.

Hours earlier, Bush demanded a Senate confirmation vote "now" on Bolton, while declining to say whether he was considering a recess appointment if Democrats continued to block such a vote.

In debate before the cloture vote, Senate Majority Leader Bill Frist (R-Tenn.) accused Democrats of "obstructing a highly qualified nominee" and thereby "doing harm to our country." Calling Bolton "a straight-shooter" and a "man of integrity," Frist argued that he "is the right man to represent us in the United Nations" and said a vote for him is a vote for reform there.

Sen. Joseph R. Biden Jr. (D-Del.), the ranking Democrat on the Senate Foreign Relations Committee, said tonight's vote was "not about John Bolton" but about the Senate's right to demand information to make its decisions, regardless of whether the executive branch deems the information relevant.

"We will agree to vote up or down on the Bolton nomination as soon as the administration provides information . . . that we have a right to obtain," Biden said in a floor speech.

Democrats are seeking materials related to Bolton's 2003 testimony on Syria and weapons of mass destruction to see whether he exaggerated intelligence data to fit his ideological convictions. They also want access to 10 National Security Agency intercepts identifying 19 Americans or U.S. companies -- information that was provided to Bolton at his request for reasons that Democrats say remain suspicious.

Biden said during debate before this evening's vote that Bolton had told him "intellectual curiosity" and "context" were why he wanted the Americans' identities, which are usually redacted from NSA transcripts distributed outside the agency. But Biden said it has been alleged that Bolton was "spying on rivals in the bureaucracy."

Sen. George Allen (R-Va.) charged that Democrats were "on a fishing expedition" against Bolton and said the effect of holding up the nomination was to "keep obstructing reform of the United Nations."

Speaking to reporters at the White House earlier in the day after a meeting with European Union leaders, Bush was asked about the prospect of using a recess appointment to install Bolton at the head of the U.S. mission to the United Nations, effectively bypassing Senate confirmation temporarily. The president did not answer directly, instead repeating his call for a confirmation vote. Secretary of State Condoleezza Rice, interviewed on "Fox News Sunday," had left open the possibility that Bolton could be named to the post during the upcoming Independence Day recess in which the Senate will be out of session from July 4 to July 11. A recess appointment by Bush would allow Bolton, currently undersecretary of state for arms control and international security, to serve as ambassador to the United Nations through January 2007.

"I think Mr. Bolton ought to get an up-or-down vote on the Senate floor," Bush said. "That's my call to the Senate. I nominated John Bolton to be the ambassador to the United Nations for a reason. . . . The American people know why I nominated him -- because the U.N. needs reform, and I thought it made sense to send a reformer to the United Nations."

The United States wants "more accountability and transparency and less bureaucracy" at the United Nations, and "John Bolton will help achieve that mission," Bush said.

"And so I think it's time for the Senate to give him an up-or-down vote, now," Bush said. "If they're interested in reforming the United Nations, they ought to approve John Bolton."

In the news briefing at the White House, Bush also strongly defended the treatment of prisoners at the U.S. naval base at Guantanamo Bay, Cuba, and he held out the prospect of eventual trials in civilian or military courts for detainees there and in other U.S. facilities abroad.

Bush, citing a briefing today by the top commander of U.S. forces in the Middle East, also said he is convinced that Iraqi security forces are becoming increasingly "battle-hardened" and are making progress in their ability to defend themselves against insurgents he described as "cold-blooded killers."

He said that despite past differences between the United States and European countries over his decision to invade Iraq in 2003, there was now general recognition of a need to work together to help Iraq's fledgling democracy succeed -- the main theme of an international conference in Brussels this week that is being attended by top Iraqi officials.

Bush made the comments after a meeting and lunch with European Union leaders including Jean-Claude Juncker, the prime minister of Luxembourg and current president of the European Council; Jose Manuel Barroso of Portugal, the European Commission president; and Javier Solana of Spain, the E.U.'s foreign and security policy chief.

In response to another question, Bush said he thinks about Iraq "every single day, because I understand we have troops in harm's way, and I understand how dangerous it is there." He added, "And the reason it's dangerous is because there's cold-blooded killers that will kill Americans or kill innocent Iraqis in order to try to drive us out of Iraq."

He said he has been getting the latest assessments on Iraq and spoke today to Gen. John P. Abizaid, the commander of U.S. forces in the Middle East.

"We're making progress toward the goal, which is, on the one hand, a political process moving forward in Iraq, on the other hand, the Iraqis capable of defending themselves," Bush said. "And the report from the field is that while it's tough, more and more Iraqis are becoming battle-hardened and trained to defend themselves. And that's exactly the strategy that's going to work. . . . And we will complete this mission for the sake of world peace."

Asked by a European reporter about the U.S. commitment to human rights in view of detentions of terrorist suspects without charge or trial at Guantanamo and in secret prisons elsewhere, Bush said nations that espouse freedom and human rights have obligations to live up to their words, "and I believe we are in Guantanamo." He urged journalists to "go down to Guantanamo" and see for themselves how detainees are treated.

Of those detained at the U.S. naval base, "about 200 or so have been released back to their countries," and some have again taken up arms, Bush said.

"There needs to be a way forward on the other 500 that are there," he said. "We're now waiting for a federal court to decide whether or not they can be tried in a military court, where they'll have rights, of course, or in the civilian courts." Bush added. "And when the courts make the decision they make, we'll act accordingly."

Many of those detained "are dangerous people," and some could still provide useful information, Bush said. He cited the detention abroad of Khalid Sheikh Mohammed, "the mastermind of the September the 11th attack that killed over 3,000 of our citizens."

Mohammed "is being detained because we think he could possibly give us information that might not only protect us but protect citizens in Europe," Bush said. "And at some point in time, he'll be dealt with, but right now we think it's best that he be kept in custody."