The protest came just days after anti-war groups on Thursday began a $1 million ad campaign on television and in newspapers accusing the Bush administration of lying about the need for an extended U.S. military presence in the Middle East.

More than 1,900 members of the U.S. military have died since the beginning of the Iraq war in March 2003.

Bush on Thursday said that withdrawing troops right now would make the world more dangerous.

Opponents of the war disagreed.

"It's always been possible to pull troops out," Bethany Malmgren of Los Angeles said in response to the president's comments. "By saying that, he's being very judgmental and not taking into consideration the needs of Iraqi people and their rights," Malmgren said.

Saturday's event was organized by A.N.S.W.E.R. (Act Now to Stop War and End Racism), whose members anticipated 5,000 people to attend the rally and march. By the time the march started, the sidewalks and Westlake Plaza were packed with people - from modern hippies to babies in strollers. At least 50 police officers were clearing the streets of cars and buses to make way for the marchers.

Jane Cutter, a member of A.N.S.W.E.R., said it was important that people demonstrate to show Bush that he has no other option but to withdraw from Iraq. Cutter, like other demonstrators Saturday, said resources are being wasted in Iraq.

"People in the gulf have been left to die while millions of dollars are being spent on the war in Iraq," she said, referring to the victims of Hurricane Katrina.

John Ferrero, 60, of Seattle, agreed and called for an investigation of the president, Defense Secretary Donald Rumsfeld and "the whole chain of command for their torture in Iraq."

Ferrero said he also was concerned about the way the war in Iraq has divided this country and caused economic devastation.

Holding signs and banners that said "Bring the troops home now," "Wage Peace" and "End colonial occupation: Iraq, Palestine, Haiti," protesters marched peacefully down Pine Street to Second Avenue, north to Marion Street and up Fourth Avenue back to Westlake Plaza.

Meanwhile, counter-demonstrations were hard to find Saturday.

Dave Loebe, 53, of Federal Way, walked quietly along the sidewalk during the march, holding a white flag with a red border and blue star in the center that said, "Honor those who serve."

With many friends in the military, Loebe wanted to show his support for them. "I do this all the time," he said, nodding to the marching crowd and saying, "They have a right to demonstrate."

Carol Isaac, 62, of Seattle, held up a sign showing Bush saying "Shut up and shop," a spoof, she said, on his comments after the Sept. 11, 2001, terror attacks.

Isaac marveled at the spectrum of people who came out Saturday, recalling her participation during the Vietnam protests when she said most protesters were "the people suffering the most, the young people."

Kent and Meredith, a couple from Portland, Ore., who gave only their first names, brought their sons, Griffin, 6, and Kegan, 15, to the rally.

"We thought it would be important for the kids to participate in this," Meredith said. "I just want them to have a wider world view than what we talk about at our dinner table."

Kegan held up a sign that said, "Bring my bro home," with a picture of a soldier dressed in desert camouflage.

The couple's 22-year-old son, who they did not want to name for his protection, is in Iraq as a medic with the California National Guard. He's due home in January.

"I just want them all home. It isn't just my son," Kent said.

He later added, "The only difference between today and the next day or the next year is the amount of dead people ... both U.S. soldiers and Iraqis."

Kegan said the march was "awesome," the president, however, is not. "Bush sucks," he shouted as he walked among baby strollers and people with dogs.

Other protests were staged in San Francisco, Los Angeles and in Washington, D.C., where tens of thousands of demonstrators marched by the White House calling for Bush's impeachment.

Bush was out of town, monitoring hurricane recovery efforts from Colorado and Texas.

And in London, an estimated crowd of 10,000 marched in support of withdrawing British troops from Iraq.