Senate Democrats are concerned about allegations that Mr. Bolton sought to shape intelligence to meet ideological ends. They have called for the administration to hand over information on the nominee's use of intelligence material during his current tenure as undersecretary of state for arms control and international security.
But the White House has refused the Democrats' request, which it characterized as a stalling tactic, and says it has already been very forthcoming with information on Mr. Bolton.
Senate Democratic leader Harry Reid is signaling that fellow Democrats will not hesitate to block the vote for a second time in two months as they stand firm on their demand for the information.
"Unless the administration changes course before this vote is held, the outcome will be exactly the same as it was last month, and it may even have less support than it did before," he said.
A procedural vote is to be held cut off debate on the nomination. Last month, the Senate fell two votes short of the 60 needed in the 100-seat chamber to end the debate and move to an up-or-down vote on the nominee.
Although there is little chance the procedural vote will succeed this time, Republicans are expected to use it to portray Democrats as obstructionist.
Senate Majority Leader Bill Frist says Mr. Bolton would be easily confirmed by the Senate, which Republicans control with a 55-seat majority, if the Democrats would allow the vote to take place.
Mr. Frist says it is essential that the United States be represented at the United Nations at a time when there are daily reports highlighting the critical need for reform at the world body:
"Whether it is the billions of dollars that have been wasted in the oil-for-food program, whether it is the tragedy that relates to the refugees and their treatment in Congo, whether it is the issues of Darfur [Sudan], which is inadequately being addressed in terms of genocide being committed there, whether it is the human rights commission in the United Nations, which has countries which we know are abusers of human rights," he said. "We need to have a strong ambassador there."
At the White House, spokesman Scott McClellan did not directly respond to questions about whether President Bush would name John Bolton as a recess appointment to sidestep Senate action. Instead, he said the administration is focused on getting the nominee an up-or-down vote.
The Constitution gives the president the power to fill vacancies during a Senate recess. Those appointments expire at the end of the next Senate session.
President Bush could give Mr. Bolton a recess appointment during Congress' Independence Day recess next month or during its month-long vacation in August.