te House in more than a decade. It is the first major rally to occur since a D.C. law that requires police to give clear warnings before arresting demonstrators took effect.

Passed in response to the much-criticized mass arrests of protesters at a downtown park in 2002, the law also restricts the use of police lines to contain nonviolent demonstrators and requires that police wear clearly identifiable badge numbers. Police also may not stop spontaneous rallies -- as long as such incidents do not clog sidewalks or violate traffic laws -- by arresting demonstrators for protesting without a permit.

Organizers said they are mobilizing nationwide for what could be the largest war protest since the U.S.-led invasion of Iraq more than two years ago. Various coalitions are organizing buses, vans and carpools to bring in protesters from across the country.

"We can anticipate 100,000 people," said Cmdr. Cathy Lanier, who supervises the police department's special operations division. "There will be mothers, grandmothers and children -- a huge, diverse group. They are very peaceful. We have been meeting with them regularly."

The umbrella organizations staging the rally -- United for Peace and Justice and the ANSWER Coalition -- say they represent thousands of people and dozens of causes. They obtained permits for public areas that can hold about 100,000 people.

Organizers are asking protesters to gather at 11 a.m. Saturday on the Ellipse, where the rally is scheduled to take place. The march will cover a stretch of streets in the blocks surrounding the White House and Justice Department and wind up at the Washington Monument, organizers said.

Counter-demonstrators, who are planning rallies before and after the antiwar gathering, are expected along the march route.

To control crowds, D.C. police officials said they will have dozens of officers directing traffic at 110 spots. Other officers will be stationed along the march route. D.C. police said staffing levels in the city's police districts will not be affected by the special deployment.

U.S. Park Police will join D.C. police in the crowd-control effort. Park Police also have canceled days off for officers who patrol the Ellipse and other federal areas where the main antiwar rallies are to be held. Scores of Park Police officers will be in uniform Saturday, including some on horseback and bicycles.

Undercover officers will mingle among demonstrators. Others in riot gear will be ready to respond to an emergency, said Park Police Sgt. Scott Fear.

"We prepare for the worst but hope for the best," Fear said. He echoed Lanier's view that police anticipate no trouble from people associated with the main antiwar groups. He said police were keeping an eye on splinter groups that could cause problems.

"Our intelligence unit has been working with other agencies to gather as much information as possible," Fear said.

Besides the rallies related to the war in Iraq, D.C. police are preparing for demonstrations at the downtown headquarters of the International Monetary Fund and World Bank, which are scheduled to hold meetings next weekend. The semiannual gatherings often draw anti-globalization and other protest groups, and D.C. police said they will close some streets and station about 300 officers near the buildings to handle crowds and traffic.

The police warning law, passed in April, came in response to police handling of another IMF-World Bank protest. In September 2002, police rounded up about 400 demonstrators and bystanders in Pershing Park and arrested them, even though they had not been given an order to disperse. This year, the District government agreed to pay $425,000 to settle a lawsuit filed by seven people who the city acknowledged were wrongfully arrested. A class-action lawsuit against the city is pending.

Lanier said there will be subtle changes in the police response next weekend, most of them not visible to bystanders. Among the differences, the department educated officers about the new law's requirements and restrictions. If officers need to don riot gear, they will be required to display badge numbers clearly on their helmets, she said.

Mara Verheyden-Hilliard, co-founder of and a lawyer with the Partnership for Civil Justice, has been working closely with police to obtain permits for the antiwar demonstration. She said she did not expect problems at the rally or with the police response. She is taking her 7-month-old son to the rally, she said.

"I think police are going to try to show that they are trying to abide by the Constitution," Verheyden-Hilliard said.

Staff writer Petula Dvorak contributed to this report.

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