On the eve of his inauguration as the United States' 44th president, Barack Obama has honoured slain civil rights leader Martin Luther King.
Mr Obama visited wounded troops at a military hospital and issued a call to Americans to remember Martin Luther King by recommitting themselves to public service.
Mr Obama visited an emergency shelter for homeless and troubled teenagers near Washington's Capitol Hill, as one of several events on the annual holiday that commemorates the civil rights leader, who was assassinated in 1968.
After rolling up his sleeves to help paint a wall at the shelter, Mr Obama touched on a theme of personal responsibility expected to figure prominently in Tuesday's speech from the US Capitol steps.
"Given the crisis that we're in and the hardships that so many people are going through, we can't allow any idle hands.
"Everybody's got to be involved," he told reporters.
Mr Obama was accompanied by the civil rights leader's son, Martin Luther King III.
In a statement on Monday, Mr Obama said: "Today, we celebrate the life of a preacher who, more than 45 years ago, stood on our national mall in the shadow of Lincoln and shared his dream for our nation.
"Tomorrow, we will come together as one people on the same mall where Dr. King's dream echoes still. As we do, we recognise that here in America, our destinies are inextricably linked. We resolve that as we walk, we must walk together."
Hundreds of thousands of visitors are streaming into Washington for festivities leading up to Tuesday's inauguration.
The BBC reports that extensive security will be in place for the inauguration, with helicopters and fighter jets patrolling the skies and snipers positioned on rooftops. Roads and bridges into Washington will be closed to traffic.