Organizers of anti-war demonstrations are preparing to storm the nation's capital this Saturday in a last-ditch effort to speak out against President Bush and a fast-approaching war against Iraq.

At the same time troops gather outside Iraq's borders, international organizations like ANSWER — Act Now to Stop War and Racism — have requested a permit for 20,000 people to join them in waging what they call an "illegal war of aggression against Iraq."

"Saturday may be the last chance for the American people to stand up and say no," said Ramsey Clark, who served as attorney general under Lyndon Johnson and has become a leader of the anti-war movement.

Organizers would not estimate how many people they are expecting, but said buses would bring marchers from 100 cities.

"The question right now is whether the Bush administration can succeed in a race to war before public opinion finally overwhelms the war-makers and their allies," Brian Becker, co-director of the International Action Center, said at a news conference Wednesday.

But while anti-war protesters make a visible display against war, public opinion has sided with the president. Polls show close to two-thirds of Americans approve of a war with Iraq, although many would prefer to have U.N. approval before a military action begins.

White House press secretary Ari Fleischer said Wednesday that "the American people overwhelmingly feel Iraq is a threat."

With anti-war protests expected in other major cities including San Francisco, Los Angeles, and several European centers, District of Columbia officials also expressed concerns cost and security of holding demonstrations downtown.

In Washington, Mayor Anthony Williams said security is his top priority, especially in light of the national situation related to a possible war in Iraq. Williams has not stated his position on war, but the D.C. City Council passed a resolution opposing it.

The cost of coping with anti-war demonstration also has put a strain on the city's budget, according to Washington Deputy Mayor Margaret Kellems. Kellems said that $15 million has been set aside to offset local costs. Kellems went on to say that heightened security is also forcing the city to pay mounting overtime wages to those first responders such as the metropolitan police.

Metro police are ready to work with the anti-war demonstrators to make sure the march to the Justice Department goes as smoothly as possible. Sergeant Joe Gentile said police have worked with these organizations in the past to avoid problems.

Fox News' Justin Fishel and The Associated Press contributed to this report.