Anti-war activist Cindy Sheehan, center, delivers a letter to the White House, Wednesday in Washington, D.C. Sheehan, whose son was killed in Iraq last year, is calling for the immediate return of troops from the region. Her 25-state tour is set to culminate Saturday with an anti-war march in Washington.

Washington ? Anti-war activist Cindy Sheehan pledged Wednesday to “force change to happen” during protest speeches outside the White House and Capitol.

Sheehan arrived in Washington after a three-week cross-country bus tour that began near President Bush’s ranch in Crawford, Texas. She is expected to participate in a rally Saturday protesting the war in Iraq that organizers hope could draw tens of thousands of people.

Sheehan, whose 24-year-old son, Army Spc. Casey Sheehan, was killed last year in Iraq, wants Bush to more fully justify the war and say what steps he will undertaken to end it.

“This is where we will force change to happen because we the people of America are the checks and balances on this government,” she said. “And we will end this war.”

Sheehan’s one-woman protest in Texas this August re-energized the anti-war movement as well as supporters of the U.S.-led invasion and of American troops serving in Iraq. Rallies in opposition to the anti-war protesters also are set for this weekend in the capital.

“I think she should go home,” said Leslie Denunzio, a tourist from Los Angeles who was standing outside the White House when Sheehan’s contingent arrived to drop off a letter addressed to Bush.