"We are turning the corner in bringing forward a mass movement of resistance to drive out the Bush regime," said organizer Travis Morales with the activist group World Can't Wait.

Some dressed in costume, including a hooded prisoner in an orange jumpsuit, a devilish rendition of President Bush and two grim reapers. One man wore a red cheerleader outfit with "Radical" emblazoned on the jersey.

The demonstrators held up yellow police tape along a three-block stretch in front of the White House.

Thousands of protesters clogged New York City's streets as they marched from the United Nations headquarters. Some people lay down in the middle of the street, while others carried signs saying "Expose 9/11" and "This war should be over." They also handed out fliers reading, "Drive out the Bush regime."

Lydia Sugarman, 82, of Manhattan, said she believed in the power of demonstrating.

"That's how we got our civil rights," she said. "If we didn't protest we wouldn't be Americans."

White House spokeswoman Nicole Guillemard defended the administration's Iraq policy.

"Our constitution guarantees the right to peacefully express one's views. The men and women in our military are fighting to bring the people of Iraq these same rights and freedoms," she said. "The president believes it is important to stay on the offense in Iraq."

World Can't Wait was founded in 2005 and has organized several marches since then, including a nationwide protest coinciding with Bush's State of the Union address in January, according to the group's Web site. Supporters listed on the site include Edward Asner, Ed Begley Jr. and Jane Fonda and activists such as the Rev. Jesse Jackson, the Rev. Al Sharpton and Cindy Sheehan.

In Seattle, a person carrying a rifle wrapped in a blanket was among five people arrested. The charges against the other people ranged from resisting arrest to assault.

"They're still investigating to determine what that person was doing with the rifle," said Seattle Police spokeswoman Debra Brown.

The march through Seattle's streets was peaceful as protesters chanted, waved signs and wore costumes mocking administration officials. One woman dressed as a pageant queen with a sash that read, "I Miss America."

In Portland, Ore., at least 10 people were detained because they did not follow police instruction to get out of the street during a protest march through downtown.

Cathe Kent, a police spokeswoman, said one person, 26-year-old Christopher Knudtsen, also faced a charge of attempted assault for trying to attack a police officer.

An estimated 800 people, mostly college age, chanted "Impeach Bush" and carried signs, including one that read: "We Can't Wait for 2008."

Hundreds marched in Los Angeles, carrying caskets draped in U.S. flags to a federal courthouse, where protesters held a mock marriage of church and state.

In Asheville, N.C., dozens of University of North Carolina students walked out of classes. In Chicago, thousands of people flooded Michigan Avenue waving anti-Bush signs.