Coretta Scott King told a packed crowd of about 1,000 at Ebenezer Baptist Church to honor the memory of King, who would have turned 74 last Wednesday. The federal King Day holiday, first celebrated in 1986, is on the third Monday in January.
"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," King 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."'
Her comments came as the United States is considering military action against Iraq.
The daylong celebration of King's birthday was marked with memorials, church services and reflection. The ceremony at Ebenezer Baptist Church opened with songs and hymns, including "The Star-Spangled Banner" and "Lift Every Voice and Sing."
Sen. Zell Miller of Georgia referred to King as a "native son of Georgia who changed my life, the life of my grandson and your life ... and the life of an entire nation, indeed the world, for the better. We must never forget that one person, only one person can make a difference."
Miller, a Democrat, said King was a leader whose dreams still inspire people worldwide every day.
"As we pause on this day to remember this great and noble man, let us all ask ourselves again the question ... What are you doing for others?" Miller said.
President Bush invoked the legacy of Dr. Martin Luther King in calling for more government support for faith-based programs -- one of several efforts by people across the political spectrum to back their beliefs with King's blessing.
President Bush and first lady Laura Bush went their separate ways to mark the holiday. The president attended a service at the large, predominately black First Baptist Church in Glenarden, Md.
"It is fitting that we honor Martin Luther King in a church," Mr. Bush said, "because I believe, like you, that the power of his words, the clarity of his vision, the courage of his leadership, occurred because he put his faith in the Almighty."
"Even though progress has been made," he said, "there is still work to do. There is still prejudice. … There's still a need for us to hear the words of Martin Luther King so that the word of hope reaches everywhere in the land."
"As we remember the dream of Martin Luther King, and remember his clear vision for a society that's equal, a society full of justice, this society must remember the power of faith," Mr. Bush said. "This government of yours must welcome faith, not discriminate faith, as we deal with the future of this great country."
Mrs. Bush was to celebrate the federal holiday with a speech to an awards dinner of the Congress of Racial Equality. Mrs. Bush's remarks to the national civil rights group would focus on King's service to the country, White House spokesman Ari Fleischer said.
The holiday finds Mr. Bush at odds with the current civil rights establishment. Many black leaders think he should have acted more quickly to oust Senate GOP leader Trent Lott, a Mississippi Republican, for making racially-charged remarks.
And they call last week's Supreme Court brief from Mr. Bush opposing the University of Michigan affirmative action plan a "slap in the face."
Democrats have also been critical of the president's contention that the University of Michigan's admissions policies are unconstitutional.
Senate Minority Leader Tom Daschle was to outline the Democrats' civil rights agenda during a speech. The party has been focusing on the issue ever since Lott's remarks last month. Daschle was expected to again defend affirmative action during his speech to an organization of Detroit-area churches.
Senate Majority Leader Bill Frist, R-Tenn., was scheduled to attend the Congress of Racial Equality dinner.
Democratic presidential candidates Sen. John Edwards and Sen. Joe Lieberman spoke about King's importance to history. At a rally in Detroit, Lieberman called King the "modern-day Moses."
Edwards questioned President Bush's stance on affirmative action during a speech at Research Triangle Park in North Carolina.
"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.
At the church remembrance in Atlanta, the Rev. Joseph Roberts, pastor of Ebenezer Baptist Church, said a war with Iraq would dishonor King's legacy.
"Have we learned nothing from this man of peace?" Roberts said. "How can we think of destroying a people who've done nothing to us except not obey us?"
The Reverend Al Sharpton said President Bush's policies dishonor the memory of Martin Luther King.
At a worship service in Columbia, South Carolina, the Democratic presidential hopeful denounced Bush's decision to oppose the University of Michigan's affirmative action admissions policy.
He said ending that policy would "rob King's children of higher education."
Sharpton said King, who opposed the war in Vietnam, also would oppose President Bush's threatened war against Iraq.
Hundreds of activities are planned across the country for the 17th celebration of the national holiday in King's memory and the anniversary will be marked in more than 100 countries around the world.
The divergence of viewpoints articulated in King's name reflected the breadth of his activism, some say. While best known for leading efforts to end segregation and promote racial equality, King in his latter years was also a forceful advocate for economic equality and a vocal opponent of the Vietnam War.
In Atlanta, a white Catholic priest from a mostly black parish in Chicago was to give the keynote address at that city's Martin Luther King birthday commemoration.
Father Michael Pfleger says Americans should commit to take up the mantle of King's challenge — to make certain the nation lives up to its values of freedom and equality. He says this means blacks, other minorities and the poor shouldn't bear the greatest burdens in a troubled economy.
Many of the approximately 1,000 anti-war protesters who rallied Sunday near the White House invoked King's legacy.
Heather Williams, 30, of Alexandria, Va., held a sign that said: "We still have a dream."
"We don't believe in war," she said. "We don't believe in death and violence."
Some of the other observances planned in this country include: