Senate Democrats pushed back hard Tuesday against President Barack Obama’s funding request to close the Guantánamo Bay, Cuba, military prison.

After initially agreeing to provide $80 million in the $91.3 billion supplemental war spending bill for the closure, Democratic leaders reversed course Tuesday and not only decided to ax the funding, but also resolved to prohibit Obama from ever bringing Guantánamo detainees into the United States.

Though leaders said they support the decision to close Guantánamo, they argued that the White House had put them in the untenable position of defending a policy without a plan. Obama has set a deadline for the end of the year for closing the facility, but has yet to outline his plan for where to transfer hundreds of suspected terrorists, including the alleged mastermind of the 9/11 attacks — Khalid Sheikh Mohammed.

“The feeling was at this point we were defending the unknown,— Senate Majority Whip Dick Durbin (D-Ill.) said. “We were asked to defend the plan that hasn’t been announced.—

Senate Majority Leader Harry Reid (D-Nev.) said the decision to close Guantánamo was “the right one,— but he vowed that Obama would get no funding for the closure until he tells Congress what his plan is.

“Part of what we don’t want is them being put in prisons in the United States,— Reid said. “We don’t want them around the United States.—

But in what could be a potential Democratic leadership split, Durbin said he would support the transfer of detainees to U.S. prisons, particularly if they were being brought temporarily to stand trial for the crimes they may have committed. And he noted that U.S. prisons already house dangerous terrorists without endangering national security or the safety of local communities.

The Senate began debating the supplemental on Tuesday afternoon, and Senate Appropriations Chairman Daniel Inouye (D-Hawaii) was expected to offer an amendment saying that no money from the supplemental “or any other Act may be obligated or expended— for the transfer or incarceration of any detainee in the U.S. It would also prohibit Obama from constructing or renovating any existing U.S. prison in order to house Guantánamo detainees.

“This is neither the time nor … the bill to do this,— Reid said. “Democrats under no circumstances will move forward without a comprehensive plan from the president. … Under no circumstances will we allow terrorists to be released into the United States.—

Durbin said Democrats have been privately complaining to the White House about the lack of a plan for detainee transfers, but have gotten little information on when one will be forthcoming.

“We’ve been raising it for some time,— said Durbin, who noted the response has been, “They’re working on a plan.—

Still, Durbin, who is personally close to Obama, tried to play down the divide with the administration, which requested the funding.

“They understood and [the Majority Leader] apprised them of our plan,— he said.

Democratic aides agreed that the leadership essentially decided to strip the funding because they did not see the need for Members to take politically difficult votes on the issue. And it appeared that leaders would have had a difficult time actually finding the votes to beat back expected GOP amendments to strip the money or bar terrorism detainees from entering the U.S.

Even consistently loyal Democrats said the president’s request was badly timed.

“I think this money was premature,— Senate Intelligence Chairman Dianne Feinstein (D-Calif.) said. Feinstein indicated that Republican attacks on the dangers of housing terror suspects in U.S. prisons caused the Democrats to backtrack on the funding, even as she argued that cutting the money was the right thing to do now.

“I think Americans don’t know that we already have major terrorists and serial killers housed in supermax federal prisons from which no one has ever escaped and is not in anyone’s community,— Feinstein said. She added that the GOP’s argument is “just a lot of bull, but it’s a problem because it gets people upset.—

Republicans welcomed the news that Democrats were backpedaling.

“Now I understand our friends on the other side of the aisle are — shall I say — moving in our direction rapidly on this issue,— Senate Minority Leader Mitch McConnell (R-Ky.) said.

Still, McConnell said Democrats were not going to avoid tough votes just because the funding would not be in the bill. McConnell himself offered an amendment Tuesday that would require the administration to do a “threat assessment— on every detainee at Guantánamo. That assessment would have to include whether the detainee is likely to become a repeat terrorism offender.