Politicians, civil rights leaders and ordinary Americans commemorated the life and death of Martin Luther King Jr on Friday, 40 years after he was assassinated at the age of only 39. ( dpa )
President George W Bush said the anniversary was a time to celebrate King's "powerful and eloquent message of justice and hope" but said the struggle for racial equality that began with King and the civil rights movement had not yet ended.
"As we reflect upon Dr Kings life and legacy, we must recommit ourselves to following his lasting example of service to others," he said in a statement.
But some of the ongoing racial tensions were on display as Republican presidential candidate John McCain was heckled when he spoke outside the Lorraine Hotel in Memphis, Tennessee, where King was shot by a sniper as he stepped out for a breath of fresh air.
McCain apologized to the crowd for not initially supporting a federal holiday celebrating King's life, drawing some boos from the crowd largely made up of African Americans, while others called out "we forgive you."
"I remind you that we can all be a little late sometimes in doing the right thing, and Dr King understood this about his fellow Americans," McCain said.
King's birthday became a holiday in 1986. Funds are now being raised for a King monument alongside those of US presidents on Washington's National Mall - where he gave his most famous speech, "I have a dream," in 1963 during the famed march on Washington.
Democratic contender Barack Obama, vying to be the first African American president, held a moment of silence at a rally in Indiana and said he had spoken to King's family to offer his thoughts.
Obama said King fought to improve the "opportunities that should be available to all races."
Hillary Clinton, Obama's rival for the Democratic nomination, described how she was able to shake the hand of King at an event in Chicago when she was only 14 years old.
"He just took it and looked in my face and thanked me for coming," she said at a stop in Memphis. "That Dr King had such a lasting impact on a young white girl tells us something about the reach and power of his vision."