Protesters called on congressional lawmakers yesterday to stop a war in Iraq before it starts, singing "We Shall Overcome" on the Capitol's West Lawn and crossing police lines in a solemn day of antiwar actions.

Unlike Saturday's antiwar march in Washington that drew tens of thousands, yesterday's protest emphasized not large numbers but planned arrests. So at 11 a.m., after a rally at a Southeast Washington church and a march down Pennsylvania Avenue to the Capitol, the first three of dozens of protesters took a few steps into a restricted zone on the lawn and were placed under arrest.

Among them was Robert McIlvaine, whose 26-year-old son was killed Sept. 11, 2001, in the terror attack on the World Trade Center. McIlvaine, who held a white sign to his chest reading "Not in my son's name," was one of four relatives of Sept. 11 victims who took part in the protest. "We love you," protester Medea Benjamin called out to McIlvaine as he was led away in plastic handcuffs.

The demonstration kicked off a weeklong series of rallies and acts of civil disobedience targeting Congress. The events, which include more traditional forms of lobbying, were designed to urge lawmakers to repeal the October legislation that "Bush has been using as his authorization for war," said Ted Glick, 53, an organizer with United for Peace and Justice, one of many antiwar groups behind yesterday's protest. Organizers estimated the crowd at 250.

Many activists said the day's events signaled a change in tone for Washington antiwar demonstrations, as more and more men and women step forward to get arrested. The president has "organized a monster," said the Rev. Graylan Hagler, 49, pastor of Washington's Plymouth Congregational United Church of Christ. "We were asleep, but now we are wide awake."

Benjamin, a 50-year-old San Francisco mother of two, said that the protesters on the lawn "feel abandoned by our representatives. . . . We feel betrayed and we feel desperate." A few minutes after McIlvaine was arrested, Benjamin, co-founder of Code Pink: Women for Peace, which has held a daily vigil at Lafayette Square since November, crossed the line, too.

Capitol Police said 54 protesters were arrested. They included college students from North Carolina and Wisconsin, three physicians and a Catholic priest from New York, organizers said.

Officers had told protesters that they would be allowed to gather on the West Lawn though they lacked a permit. A long line of officers on foot and horseback blocked access to the building's west steps, and protesters had been warned that they would be arrested if they moved beyond the designated zone. The arrests were conducted quietly and without incident, as protesters approached the line in threes and fives. Officials said they were arrested for crossing a police line, a misdemeanor.

Capitol Police Chief Terrance W. Gainer, whose department was out in full force yesterday, said protesters were cooperative. "This is what should happen," he said of the protest. "This is the people's Capitol."

Though plans are still in the works, more acts of civil disobedience are in store for Washington this week, organizers said. Roughly 10,000 people in about 50 cities, including 500 in the Washington area, have vowed through the Iraq Pledge of Resistance campaign to commit nonviolent civil disobedience should the United States attack Iraq. The campaign is set to begin today.

U.S. Capitol Police arrest demonstrators who used civil disobedience to force their own arrests on the West Lawn of the Capitol after marching from Southeast Washington.