Civil rights leaders and politicians around the nation observed Martin Luther King Jr. Day on Monday, many of them invoking his name in arguing against war with Iraq and urging the Supreme Court to uphold affirmative action in college admissions.

King's widow, Coretta Scott King, addressed a crowd of about 1,000 at King's former pulpit, Ebenezer Baptist Church in Atlanta. She called on world leaders to settle their differences peacefully.

"We commemorate Martin Luther King Jr. as a great champion of peace who warned us that war was a poor chisel for carving out a peaceful tomorrow," she said. "We must pursue peaceful ends through peaceful means. Martin said: 'True peace is not just the absence of tension, it is the presence of justice."'

The pastor of Ebenezer Baptist, the Rev. Joseph Roberts, said a war with Iraq would dishonor King's legacy. "Have we learned nothing from this man of peace?" Roberts asked.

The civil rights leader would have turned 74 last Wednesday. He was assassinated in 1968.

During the King Day march through the historic Sweet Auburn district where King grew up, signs that read, "War is not the answer," and "Drop Bush, not bombs," rose above the sea of heads. Marchers sang "We shall overcome" to protest military action against Iraq.

Another 5,000 people marched in Seattle, including World War II veteran O'Kelly McCluskey, who carried a "Veterans for Peace" sign.

"We grandfathers have a duty to pass on what we've learned in this life," he said. The pointlessness of war is "one of the most essential lessons."

One of the largest King Day events was in Denver, where more than 30,000 people paid tribute to King and protested military action against Iraq.

"Saddam Hussein is a scary person," said Vicki Rottman of the anti-war group Women in Black Standing in Silence for Peace. "What is scarier to me is that our country in this instance may be the aggressor."

Geraldine Phillips, who grew up in a segregated Los Angeles, said she came to her city's parade to honor a man who led the civil rights battle.

"I'm enjoying my life now and Martin Luther King has got a lot to do with it," said Phillips, 78.

Many simply remembered the way things were before the civil rights movement.

"He did so much for us," said Tiffany Smile, 20, a junior at New York's State University at Purchase. "God only knows where we'd be without him."

President Bush, speaking at a Baptist church in Landover, Md., said there is still work to do to realize King's dream of equality in America. "There's still prejudice holding people back," he said.

But Bush's stance on affirmative action was questioned by Democratic presidential candidate Sen. John Edwards. Last week, the administration asked the Supreme Court to declare the University of Michigan's affirmative action admissions policies unconstitutional.

"We should support efforts that increase diversity and put an end to systems, like legacy admissions, that give special preference to the most advantaged at the expense of diversity," Edwards said in North Carolina.

Marchers in Boston sang gospel songs and carried flags and banners.

"We're here because Martin Luther King was a man of God," said Caring Hands Silva, a leader of the Natick Praying Indians, descendants of a tribe converted to Christianity in 1651. "What he represents is peace and brotherhood and love for all mankind."

In York, Pa., five white supremacists marched in opposition to King Day and in memory of a white police officer killed during the city's 1969 race riots.

"We said 'No' to affirmative action whether it's Martin Luther King trying to win favoritism for minorities or protesters trying to shout me down," said the group's leader, Richard Barrett. Hundreds of police officers were on patrol as protesters tried to drown out Barrett's speech.

Attendance was down 15 percent in a Virginia school district that held classes Monday to make up a snow day. Chesterfield Superintendent Billy Cannaday Jr., who is black, said the district needed to give students enough instruction to prepare them for standardized tests in March.

Tracey James, who brought her 12-year-old daughter to a King Day event, said she thought it was unfair the district made her choose between keeping her daughter out of school and teaching her something about the holiday.

"My child is an honor student and hasn't missed a day this year," she said.

Speaking from the same pulpit in Montgomery, Ala., where King helped launch the civil rights movement with his leadership of the Montgomery bus boycott in 1955, Alabama Gov. Bob Riley was inaugurated with a promise to end racial division.

"Alabama needs to be the state that brings it to a culmination," Riley said. "Alabama is going to lead this nation in uniting the races once and for all."

Riley later attended, without speaking, a ceremony paying tribute to Confederate Gen. Robert E. Lee, whose birthday is observed the same day as King's in Alabama.