“If they don’t [agree to restrictions], it’s not us taking away the bridge fund, it’s them taking away the bridge fund,” Reid told reporters at the unveiling of a Joint Economic Committee report estimating that the cost of the war could exceed $3.5 trillion if the current course of the war continues. The White House dismissed the report.

When asked if Congress would force the Bush administration to move money around in its annual spending measure to pay for the war if the Senate does not reach the 60 votes that will likely be needed for passage, Reid responded, “That’s right.”

Reid’s warning sets up a high-stakes showdown this week over the Iraq war. The House will try to pass an interim bridge fund with a goal for withdrawal as soon as Wednesday, and the Senate is expected to follow suit soon after. But if Republicans require Democrats to win 60 votes for passage, there probably won’t be enough support for the bill to pass the Senate.

That is certain to open up a heated partisan exchange over who is to blame for a potential lack of funds for troops in the field.

Democrats say that the $459 billion Pentagon appropriations bill, which Bush signed into law Tuesday, has more than enough funds to last until next spring.

“There have been a number of reports that have said the military can do just fine until April,” Reid said.

Sen. Charles Schumer (D-N.Y.) said that forcing the White House to spend money from the appropriations legislation would be “the first time the Iraq war is actually paid for” because funding has traditionally been allocated on an emergency basis.

But Republicans and the White House are certain to ramp up their criticisms of Democrats if the $50 billion bridge fund is sent to the president’s desk with restrictions.

“The president has made it clear that strategic decisions should be left to our military commanders,” said Sean Kevelighan, a spokesman for the White House budget office. “Congress should stop playing politics with funding for our troops on the field in harm's way.”