On the fourth anniversary of his famous "Mission Accomplished" appearance on an aircraft carrier, U.S. President George Bush has vetoed a bill that would have seen U.S. troops withdrawn from Iraq.

Speaking from the White House on Tuesday evening, Bush said the bill would create a "rigid and artificial deadline" regardless of the situation on the ground.

"It makes no sense to tell the enemy when you're withdrawing," he said.

Such a move would demoralize the Iraqi people and embolden militants across the Middle East "and send a signal that America will not keep its commitments," he said.

"Setting a deadline for withdrawal is setting a date for failure, and that would be irresponsible."

However, he extended an olive branch to Democratic leaders in Congress. He will be meeting with them Wednesday to discuss amending the bill.

"It is going to be quite a political summit at the White House tomorrow," CTV's Tom Clark told Newsnet from Washington. "This is going to be the brokering session where America decides what to do next in Iraq."

The showdown was inevitable, he said, because the Democrats -- who took control of both Houses of Congress in last November's mid-term elections -- see themselves as having a mandate to take a new approach on Iraq.

Tuesday was a significant milestone in the Iraq conflict -- for opponents of the war.

On May 1, 2003, Bush proclaimed that "major combat operations in Iraq have ended." He made the announcement while on the deck of the USS Abraham Lincoln, which was just off the coast of San Diego, Calif. at the time. A huge "Mission Accomplished" banner hung in the background.

Since then, the death toll for U.S. soldiers has hit more than 3,300, Iraq remains racked by insurgent and sectarian violence, and Bush's popularity among the electorate has shrunk by about half.

White House press secretary Dana Perino accused Democrats of playing games by sending the bill on the anniversary.

"It's a trumped-up political stunt that is the height of cynicism," she said.

The Democratic-led Congress held a ceremony Tuesday afternoon to send the bill to Bush. The bill would see U.S. troops withdrawn by Oct. 1.

"This legislation honours the sacrifice of our men and women in uniform," Nancy Pelosi, speaker of the House of Representatives, said at the ceremony in the Capitol.

Sen. Harry Reid, D-Nev., the Senate majority leader, said Bush has placed American troops in the middle of a civil war.

"After more than four years of a failed policy, it's time for Iraq to take responsibility for its future," Reid said. "Today we renew our call to President Bush: There is still time to listen. There is still time to sign this bill and change course in Iraq."

Bush plans to veto it soon after he returned to Washington from Florida. The White House said Bush would make a TV statement at 6:10 p.m. EDT, which is just before the U.S. network newscasts.

The Democrats don't have enough votes to override Bush's veto, so they are considering a compromise that would fund the current effort without giving Bush a blank cheque.

The revised bill is expected to contain benchmarks for Iraqi government performance, but it isn't clear what would happen if the Iraq government failed to meet its obligations.

With files from The Associated Press