Anti-war protesters are gearing up for what they say could be the last chance for Americans to prevent the Bush administration from attacking Iraq to oust President Saddam Hussein from power.

People from 200 cities in 40 states will celebrate Martin Luther King's birthday weekend -- and the twelfth anniversary of the Gulf War -- by traveling to the nation's capital and San Francisco to protest.

Coordinated demonstrations will take place in 32 countries, including Egypt, Belgium, Spain, Canada, Italy, Japan, Indonesia, Britain, Germany, Austria and Russia.

International protests will target Pentagon bases, and in some places -- such as in Britain, Germany, Italy, South Korea and Spain -- activists will try to carry out inspections of the facilities for U.S. weapons of mass destruction.

Other ambitious domestic weekend rallies are planned in Phoenix, in Portland, Ore., and in Tampa, where protesters planned to gather outside the headquarters of the U.S. Central Command, the arm of the Pentagon that would direct the Iraq war. In Pittsburgh, activists were hoping to draw several thousand to Jan. 24-26 protests.

In Washington, marchers will have to bundle up. Temperatures won't get above the 20s on Saturday and snow flurries are expected for Sunday.

Protesters there will gather at the west side of the Capitol Building on one end of Pennsylvania Avenue for a brief rally beginning at 11 a.m. Scheduled speakers include actress Jessica Lange, Vietnam veteran and author Ron Kovic, former representative Cynthia McKinney, D-Ga., and others from labor, peace and Muslim organizations.

That will be followed by a march to the Washington, D.C., Navy Yard, within walking distance from the Capitol.

Counter-protesters, including the D.C. chapter of the national organization Free Republic, a frequent counter-presence at protests, and MOVE-OUT! (Marines and Other Veterans Engaging Outrageous Un-American Traitors), will rally at Constitution Gardens on the Mall at 9 a.m. Saturday and later greet marchers outside the U.S. Marine Corps barracks.

But President Bush himself won't be home. He's scheduled to leave Friday afternoon for his Camp David presidential retreat in Maryland.

"We've been working with protest groups; they've got permits for various locations, including marches, so we'll be ready for it," said District of Columbia Police Chief Charles Ramsey. "We don't anticipate any problems, although we do anticipate large crowds."

In San Francisco, where it will be in the low 60s and partly cloudy, organizers are expecting 80,000 people to turn out for Saturday's anti-war march and rally. The rally will feature speeches by Rep. Barbara Lee and Rep. Lynn Woolsey -- both Democratic U.S. House members representing California -- and others. Beginning at 11 a.m., marchers plan to gather at Justin Herman Plaza and then head up Market Street toward the Civic Center. A rally will begin at 1 p.m.

The city's police department assigned extra patrol, tactical and motorcycle officers to the rally.

Also in San Francisco, more than a hundred drivers of electric and hybrid vehicles, bearing bumper stickers saying, "Real Patriots Drive Hybrids," will meet the San Francisco Bicycle Coalition to form an anti-war convoy.

Protesters in the organization Baring Witness, which specializes in "naked resistance," said they might take their clothes off and march down San Francisco's Market Street.

In Tampa, Fla., this weekend's events include a prayer service and a peace gathering, largely composed of religious groups, at the gates of MacDill Air Force Base from 1 to 4 p.m.

In Oregon, dozens of people on Saturday are expected to march across the Columbia River to Portland. At 12:30 p.m., the march and rally will start in south Park Blocks. Vancouver, Ore. will first have its own march at 10:15 a.m. Participants will walk silently from Clark College into downtown.

On Sunday, young demonstrators from 400 schools and colleges will hold another march in Washington, D.C., beginning at 11 a.m. in front of the Justice Department. They will travel to the White House to push for weapons inspections here in the United States.

Although the holiday weekend's demonstrations aren't likely to be the last such stand against military action in Iraq and alleged civil liberties violations here at home, anti-war leaders say it may be the last chance to have their voices heard before war is declared.

The Associated Press contributed to this report.