WASHINGTON – President Bush vetoed legislation to pull U.S. troops out of Iraq Tuesday night in a historic showdown with Congress over whether the unpopular and costly war should end or escalate.

It was a day of high political drama, falling on the fourth anniversary of Bush’s “Mission Accomplished” speech declaring that major combat operations had ended in Iraq.

In only the second veto of his presidency, Bush rejected legislation pushed by Democratic leaders that would require the first U.S. combat troops to be withdrawn by Oct. 1 with a goal of a complete pullout six months later.

“This is a prescription for chaos and confusion and we must not impose it on our troops,” Bush said in a nationally broadcast statement from the White House. He said the bill would “mandate a rigid and artificial deadline” for troop pullouts, and “it makes no sense to tell the enemy when you plan to start withdrawing.”

Democrats accused Bush of ignoring Americans’ desire to stop the war, which has claimed the lives of more than 3,350 members of the military.

“The president wants a blank check,” said House Speaker Nancy Pelosi, D-Calif., moments after Bush’s appearance. “The Congress is not going to give it to him.” She said lawmakers would work with him to find common ground but added that there was “great distance” between them on Iraq.

The legislation amounted to a rare rebuke of a wartime president and an assertion by Democrats that Congress must play a major role in Iraq and the extent of U.S. involvement.

Senate Majority Leader Harry Reid said Bush has an obligation to explain his plan for responsibly ending the war.

“If the president thinks by vetoing this bill, he’ll stop us from working to change the direction of the war in Iraq, he is mistaken,” Reid said.

Lacking the votes to override the president, Democrats have already signaled they intend to approve a replacement bill stripped of the troop withdrawal timetable. Determined to challenge Bush’s policy, they are turning their attention to setting goals for the Iraqi government to meet as it struggles to establish a more secure, democratic society.

The White House and congressional Republicans have also called for so-called benchmarks, but only if they don’t mandate a troop withdrawal or some other major change in war policy.

Bush will meet with congressional leaders – Democrats and Republicans alike – on Wednesday to discuss new legislation.

He said Democrats had made a political statement by passing anti-war legislation. “They’ve sent their message, and now it’s time to put politics behind us and support our troops with the funds,” the president said.

He said the need to act was urgent because without a war-funding bill, the armed forces will have to consider cutting back on buying or repairing equipment.

“Our troops and their families deserve better, and their elected leaders can do better,” Bush said.

“Whatever our differences, surely we can agree that our troops are worthy of this funding and that we have a responsibility to get it to them without further delay,” the president said.

Bush signed the veto with a pen given to him by Robert Derga, the father of Marine Corps Reserve Cpl. Dustin Derga, who was killed in Iraq on May 8, 2005. The elder Derga spoke with Bush two weeks ago at a meeting the president had with military families at the White House.

Derga asked Bush to promise to use the pen in his veto. On Tuesday, Derga contacted the White House to remind Bush to use the pen, and so he did. The 24-year-old Dustin Derga served with Lima Company, 3rd Battalion 25th Marines from Columbus, Ohio. The five-year Marine reservist and fire team leader was killed by an armor-piercing round in Anbar province.

Minutes after Bush vetoed the bill, an anti-war demonstrator stood outside the White House with a bullhorn: “How many more must die? How many more must die?”

Earlier at the Capitol, Democrats held an unusual signing ceremony of the $124.2 billion bill before sending it to the White House.

“The president has put our troops in the middle of a civil war,” said Reid. “Reality on the ground proves what we all know: A change of course is needed.”