The lawsuit in federal district court claims the National Park Service is illegally blocking the general public from access to vast portions of Pennsylvania Ave. reserved solely for guests screened by the Presidential Inaugural Committee.

"The public has the right to access the parade, but what they are doing is trying to sanitize the parade route," said Mara Verheyden-Hilliard, an attorney representing the A.N.S.W.E.R. Coalition and other activists.

Park Service officials say they have fulfilled their obligation to allow the public - including demonstrators - access to open areas along the parade route. The agency has offered A.N.S.W.E.R. space for up to 10,000 protesters to stand or sit in bleachers in a large plaza along the route, just a few blocks from the Capitol.

The park service also has issued A.N.S.W.E.R. permits for protesters to stand in nine other smaller locations along Pennsylvania Ave. But the group says most of those areas are tiny pockets behind bleachers or in fenced-in areas more than 100 feet from the parade route.

In 2001, thousands of demonstrators were able to stand on sidewalks along the parade route, carrying signs and shouting slogans as Bush's motorcade passed. This year, Verheyden-Hilliard said, the park service is excluding the public from most sidewalks and open spaces between and around bleachers.

The lawsuit seeks an injunction to order the park service to open up Pennsylvania Ave., to all members of the general public, including protesters. Verheyden-Hilliard said a federal judge could hear arguments in the case on Friday or early next week.

A.N.S.W.E.R is also challenging Secret Service restrictions that allow protesters to carry signs, but ban them from being affixed to poles or sticks.

The parade gets under way at 2 p.m. EST on Thursday after Bush's swearing-in at the Capitol and a celebratory luncheon.