Democrats lined up with Republicans in the 90-6 vote that came on the heels of a similar move a week ago in the House of Representatives, underscoring widespread apprehension among Mr. Obama's congressional allies over voters' strong feelings about bringing detainees to the U.S. Thefor Thursday on the U.S. fight against terrorism.
For symbolic effect, the speech will be at the National Archives where the Constitution is displayed, reports CBS News chief White House correspondent Chip Reid.
Mr. Obama has vowed to close the prison by January 2010, and the Senate's vote was not the final word on the matter. It will be next month at the earliest before Congress completes work on the legislation, giving the White House time pursue a compromise that would allow the president to fulfill his pledge.
But Obama's maneuvering room was further constrained during the day when FBI Director Robert Mueller told a congressional panel that he had concerns about bringing Guantanamo Bay detainees to prisons in the United States. Among the risks is "the potential for individuals undertaking attacks in the United States," said Mueller, who was appointed by President George W. Bush in 2001 and is serving a 10-year fixed term in office.
Additionally, U.S. District Judge John Bates ruled this week that some prisoners - but not all - can be held indefinitely at Guantanamo without being charged, thus increasing the pressure on the administration to develop a plan for the men held there.
After the Senate vote, White House press secretary Robert Gibbs said, "The president understands that his most important job is to keep the American people safe and that he is not going to make any decision or any judgment that imperils the safety of the American people."
He added Mr. Obama has not yet decided where some of the detainees will be sent. A presidential commission is studying the issue.
There was no suspense in the moments leading to the Senate vote, although Democrats maneuvered to take political credit for denying Obama funds he sought to close the prison. They hoped to negate weeks of Republican warnings about the danger involved.
Sen. Daniel Inouye, a Democrat and chairman of the Appropriations Committee, said he had initially favored keeping Guantanamo open until Obama produced a "coherent plan for closing the prison."
He said he was changing course and "the fact that the administration has not offered a workable plan at this point made that decision easy."
The administration asked for $80 million to close the facility. Obama promised repeatedly as a presidential candidate to shut down the prison, calling it a blot on the international image of the United States.
Even in voting to deny him the funds, Obama's Democratic allies insisted the president was fundamentally correct.
The president's supporters say critics are fear-mongering, reports Reid.
"The reality is we are holding some of the most dangerous terrorists in the world right now in our federal prisons," said Sen. Dick Durbin, D-Ill.
Like the Supermax prison in Colorado which holds among others shoe bomber Richard Reid and al Qaeda member Zacarius Moussaoui, reports Reid.
"It has 490 beds. They are reserved for the worst of the worst," said Sen. Dianne Feinstein of California. "Guantanamo is used by al Qaeda as a symbol of American abuse of Muslims and is fanning the flames of anti-Americanism around the world."
Senate Majority Leader Harry Reid, who had said on Tuesday he opposed allowing detainees to be transferred to U.S. prisons, issued a statement saying he might change his mind on that point.
The lopsided vote was a victory for the Senate Republicans, who have recently turned their attention to Obama's policies on foreign policy and terrorism after failing to make headway in criticizing his economic program.
Sen. Mitch McConnell, the Republican leader, has delivered numerous speeches in recent weeks raising pointed questions about Obama's plans to close the prison without first explaining where the men held there would be sent. "For months, we have been saying what Senate Democrats now acknowledge: that because the administration has no plan for what to do with the 240 detainees at Guantanamo, it would be irresponsible and dangerous for the Senate to appropriate the money to close it," McConnell said shortly before the vote.
Obama came to office pledging a dramatic change in George W. Bush's terrorism policy. In the months since, he has woven an uncertain course, occasionally angering liberals.
He first backed the cancellation of military tribunals for prisoners, then announced he wanted them resumed with greater legal protections for the accused. Last week, he reversed course on another issue, deciding to appeal a court-ordered release of prisoner-abuse photos taken at Abu Ghraib in Iraq.
Several Republicans praised Obama for those very steps.
"I commend him for being very willing to change his opinion in light of having access to the intelligence he didn't have access to" as a candidate, said Sen. Orrin Hatch.
FBI Director Mueller made his comments before the House Judiciary Committee.
Prodded by Rep. Jerrold Nadler, a Democrat to agree that Guantanamo detainees could be kept safely in maximum security prisoners in the United States, Mueller declined. He noted that in some instances gang leaders have run their gangs from inside prisons.