The White House expressed opposition on Friday to any attempt by the U.S. Senate to revise the 2002 resolution that President George W. Bush used to go to war in Iraq.

Senate Democrats said they were working on a proposal to rewrite the 2002 resolution to create a narrower, binding authority that would restrict the military's role and prompt U.S. troops to start pulling out.

The 2002 resolution, approved at a time when American tensions were still running high from the September 11 attacks, gave Bush fairly wide latitude.

It authorized him to use the U.S. armed forces "as he determines to be necessary and appropriate in order to defend the national security of the United States against the continuing threat posed by Iraq."

White House spokesman Tony Fratto, asked by reporters if Bush would oppose any effort to revoke the 2002 authorization, said, "Of course we would."

He said it was unclear whether Democrats would go forward with the proposal because they appeared divided on Iraq.

"I think what's clear is that there's a lot of, you know, shifting sands in the Democrats' positions right now. It's hard to say exactly what their position is," Fratto said.

But he said the White House considers the 2002 resolution still active and that to pull U.S. troops out of Iraq, as some Democrats support, "would bring chaos to Baghdad."

Bush has made clear he will fight hard for a $100 billion proposal to fund U.S. troops in Iraq and Afghanistan, with some Democrats pondering an attempt to force a change in policy by putting restrictions on how the money is spent.

After Senate Republicans halted a non-binding resolution opposing Bush's troop buildup in Iraq, the Democrats are determined to challenge Bush anew by replacing the 2002 authorization of force in Iraq with a narrower mission statement for U.S. troops, congressional aides said on Thursday.

The newly defined U.S. mission would involve denying terrorists a safe haven in Iraq, training Iraqi troops and helping Iraqis protect their own borders, said one Democratic aide. The proposal would be binding and a draft calls for U.S. troops not involved in the narrower mission to come home by early 2008, he said.

There are 139,000 U.S. troops in Iraq. Lawmakers would rely on the U.S. military to tell them how many would be needed for the narrower mission, the aides said.

The proposal is being drafted by Michigan Sen. Carl Levin, the chairman of the Armed Services Committee, and Delaware Sen. Joseph Biden, chairman of the Foreign Relations Committee, and their staffs -- with the blessing of Senate Democratic Leader Harry Reid of Nevada.

(Additional reporting by Susan Cornwell)