WASHINGTON -- In a stunning setback for President Bush, the Senate for a second time blocked a vote on his controversial nomination of John Bolton as his envoy to the United Nations.

At a White House news conference before last night's vote, Bush did not answer a question about whether he would appoint Bolton to the post while the Senate is out of town for two weeks for the July 4th holiday.

A recess appointment would put Bolton on the job until 2007 without a Senate vote. But being appointed without confirmation would greatly reduce Bolton's international stature at a time when the United States is in some disfavor with other nations within the organization.

Bush's other choices now are to release certain documents about Bolton the Democrats want or to nominate someone else. Senate Democratic leader Harry Reid of Nevada said it was up to Bush what happens next to Bolton, whom he called "this flawed candidate."

Despite Bush's insistence yesterday that Bolton was the right man "because the U.N. needs reform, and I thought it made sense to send a reformer to the United Nations," the Senate fell six votes short of the 60 needed to end debate and vote on Bolton. If that happened, he would be approved because confirmation takes only a majority of votes, which Bolton has.

Last night's 54-38 vote was even worse for Bush than the first vote of 56-42 that failed to end debate on May 27.

Sen. George Voinovich, R-Ohio, who voted against ending debate this time but for it last time, said in a statement after the vote that he has learned more about Bolton since the first vote and is even more convinced that the undersecretary of state for arms control and international security is not the right man for the U.N. job.

Voinovich said he has discussed the issue with both Republicans and Democrats, "many of whom agree with me that John Bolton's service at the U.N. will be a liability to our country and that we can do better." He said a number of senators "have made the commitment for one reason or another to vote for cloture and/or for Bolton's nomination."

Bush was asked about Bolton during a brief news conference that he held with leaders of the European Union, after a meeting with them over a host of international issues ranging from Iraq to trade.

Bush called Jean-Claude Juncker, president of the European Council, and Joe Manuel Barroso, president of the European Commission, "my friends here," and said, "The U.N. is an important organization, and the American people, I think ... will understand how important it is when the U.N. is reformed and is held to account. And so we want more accountability and transparency and less bureaucracy, and John Bolton will help achieve that mission."

Sens. Joe Biden, D-Del., and Christopher Dodd, D-Conn., who led the fight to prevent a confirmation vote for Bolton, said the issue was not his credentials, his sometimes-harsh treatment of those with less authority or his legendary brusqueness. They said the primary issue for them was the Bush administration's refusal to turn over a number of documents that referred to Bolton's past comments about Syria's interest in weapons of mass destruction and the nominee's interest in finding out the names of Americans referred to in intelligence reports.

The White House has said it is not necessary for the Senate to have those documents. Biden said that if the White House permits four senators on the Foreign Relations and Intelligence committees to see the documents in question, a vote will take place.

Biden said last night's vote was about "whether or not the Senate will let the president decide how we are to fulfill our constitutional responsibility under the 'advise and consent' clause. We should not permit the president to dictate how we should proceed."

The administration has an "obsession of secrecy." Biden said, that the Senate must not accommodate.

The documents could show, Biden said, that Bolton was interested in the names of Americans referred to in intelligence intercepts -- transcripts of conversations between Americans and foreigners -- not because of intellectual curiosity, as the nominee has claimed, but for possible retribution if they disagreed with his policies.

Democrats assert that he tried to direct the dismissal of intelligence analysts who disagreed with him. They also say he exaggerated Syria's aims in getting weapons of mass destruction and Cuba's goals to bolster his own policy objectives.

But Senate Majority leader Bill Frist, R-Tenn., said the Democrats were motivated by obstructionism. "The plain and simple truth is that some on the other side of the aisle are obstructing a highly qualified nominee and, I believe, by [their] not allowing him to assume this position yet, are doing harm to our country."

There has been no U.S. ambassador to the U.N. for five months, since John Negroponte was tapped to become director of national intelligence.

Clearly unhappy, Frist said, "John Bolton is the right man" to represent the United States, adding that he is a "straight shooter and a man of integrity." Yesterday's vote was a potential political blow to Frist, who is thought to be interested in running for president in 2008, because it was his decision to call for it without having enough support to win.

Sen. George Allen, R-Va., complained that Democrats kept "changing the goalposts" -- first opposing Bolton because of his often-stated contempt for the United Nations, then because of his treatment of employees and finally because of the disputed documents.

Although more than a hundred diplomats signed a letter opposing Bolton, Senate Foreign Relations Committee Chairman Richard Lugar, R-Ind., said Bush deserves his own person at the United Nations in troubled times, and that many consider Bolton to be "one of the smartest guys in Washington." Lugar said Bolton is one of few who have thought seriously about how to reform the U.N. after the revelations of the Iraqi oil-for-food scandal.

But Sen. Barbara Boxer, D-Calif., countered that no other president has made such a contentious nomination for the U.N. post. All but two ambassadors were confirmed unanimously, and the other two were approved by votes of more than 80 senators.