Washington has become a hub for people hoping for change
Barack Obama has called for Americans to come together for the common good, hours before he is sworn in as the first black president in US history.
Evoking the spirit of the assassinated civil rights leader Martin Luther King, he called on people to dedicate themselves to public service.
With so many people facing hardship, he said, there could be no idle hands.
At least two million people are expected to attend the inauguration in a record turnout for such an event.
The roar of approval that will greet Barack Obama when he takes the oath of office will be heard around the world and will be genuine and heartfelt and will come from all corners of America, BBC North America editor Justin Webb reports.
Mr Obama has been a hugely active and visible president-elect - probably the most active in history - and the nation has on the whole approved of his demeanour and choices, our editor says.
It will, of course, get much more difficult but to suggest that his honeymoon might be short-lived would seem at the moment to fly in the face of a general mood of optimism, he adds.
Put a different way, there is a desperate hope that someone has got some answers to America's problems, our editor says.
Mr Obama made his call on Monday, during a visit to a community project in Washington on the anniversary of the birth of Dr King.
Mr Obama was at a community centre on the eve of his inauguration
"Given the crisis that we're in and the hardships that so many people are going through, we can't allow any idle hands," he told reporters on his visit to the shelter for homeless and runaway young people.
Taking up a brush, he helped to paint a wall.
Late on Monday he attended a dinner honouring his presidential rival, John McCain, hailing him as a "courageous public servant" with a long list of bipartisan accomplishments.
Mr Obama will take the oath of office on President Abraham Lincoln's inaugural Bible at 1200 local time (1700 GMT).
He will be sworn in on the steps of the Capitol building looking across the city towards the White House.
Vice-President Dick Cheney is set to attend the inauguration in a wheelchair after pulling a muscle in his back while moving boxes.
1455 GMT (0955 EST): President Bush welcomes Barack Obama to the White House for coffee
1630 GMT (1130 EST): Obama and Vice-President-elect Joe Biden arrive at the Capitol for the official inaugural ceremony; Biden is sworn in
1700 GMT (1200 EST): Obama takes the oath of office, delivers the inaugural address
1740 GMT (1240 EST): Obama escorts Bush and former VP Dick Cheney to a departure ceremony
He was helping to move into his new home outside Washington in McLean, Virginia, when he injured himself.
The weather in Washington is forecast to be colder than average, around 0C.
With enormous crowds expected, security chiefs say they are prepared for all eventualities.
Roads and bridges into Washington will be closed to traffic, with sniffer dogs on the subway.
Thousands of armed police, soldiers and plainclothes agents will be on the streets, with snipers in position on rooftops near the Capitol building and along the parade route.
Helicopters and fighter jets will patrol the skies, and the Coast Guard will police the waterways.
Those in charge of security had some idea of what to expect after dealing with the hundreds of thousands who descended on the capital for Sunday's welcome concert, that kicked off the inauguration festivities.
Follow the inauguration on the BBC News website, with live text updates from 1400 GMT (0900 ET), streaming video from 1600 GMT, full coverage from our correspondents in Washington and reaction from across the world.
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