The world's biggest musical acts took to the stage Sunday at a massive outdoor concert on the majestic steps of the Lincoln Memorial.

Still, the star who shone the brightest was the man who sang nary a note - Barack Obama, who enthralled a crowd of 500,000 with a brief message of hope.

"Anything is possible in America," the president-elect said at the end of the 90-minute concert that featured performances from U2, Beyonce, Bruce Springsteen and Mary J. Blige.

"Despite the enormity of the task that lies ahead, I stand here today as hopeful as ever that the United States of America will endure; that the dream of our founders will live on in our time."

His remarks, which paid homage to both Abraham Lincoln and Martin Luther King Jr., were met with roars of approval and some tears from the joyous crowd who were counting down the hours until Obama's historic inauguration on Tuesday.

They represented a veritable sea of humanity, made up of people of all ages, colours and nationalities, stretching from the foot of the iconic memorial to the Washington Monument several city blocks away.

Jumbo screens were situated along the grassy stretch of land known as the Mall that links the Capitol in the east to the Lincoln Monument in the west.

Even when amassed around the screens, with the monument far away in the distance and the sound quality poor, the crowd cheered with glee whenever a performer took to the stage.

On the eve of Martin Luther King Jr. Day, U2 performed "In the Name of Love," their 25-year-old tribute to the slain civil rights leader.

Springsteen sang "The Rising," accompanied by a gospel choir dressed in brilliant red robes.

The crowd, including Obama and vice president-elect Joe Biden, writhed when Stevie Wonder, Usher and Shakira pumped out Wonder's classic "Higher Ground."

With the mammoth statue of Lincoln seemingly gazing down upon the performers, the Obamas and the Bidens sat behind a glass enclosure as they took in the spectacle under a chilly, slate-grey sky.

In addition to the musicians, actors including Denzel Washington and Tom Hanks were on hand to deliver historical readings.

For several hours before the concert, the city swarmed with people making their way to the show.

Security was tight, and there were hour-long lineups just to get onto the Mall. Not many were complaining, however, despite the cold.

"I wouldn't have missed any of this for the world," said Jennifer Ryan, 24, visiting from North Carolina. "This is history."

There was a spirit of celebration everywhere, with street rappers singing songs about Obama's historic election and vendors doing a swift business selling all manner of Obama merchandise to those heading to the concert.

One of them was New Yorker Ben Sherman, who was peddling Obama condoms in packages embossed with slogans that included "Change is Coming," "Hope is not Protection" and "Ultimate Stimulus Package."

"I am selling lots of them," Sherman said.

Despite the apparent Obama fever, the concert began with a convocation by the Right Rev. Gene Robinson, who asked the crowd to pray for "understanding that our president is a human being and not a messiah."

Obama will be sworn into office Tuesday, the first black man in history to become president of the United States.

The city of Washington has been abuzz not only with people keen to celebrate one of most significant inaugurations in their nation's 233-year existence, but also with anticipation about his inaugural address.

A gifted orator, Obama invoked history and hope during his speeches on a train ride from Philadelphia to D.C. on Saturday to kick off four days of inauguration festivities.

His chief of staff, Rahm Emanuel, said Sunday that Obama's address will call on Americans to embrace a new era of responsible behaviour - in both government and business.

He will ask citizens to reject the "culture of anything goes" and restore a national value system that honours responsibility and accountability, Emanuel said.

That appeal is reminiscent of John F. Kennedy's call for personal sacrifice in his 1960 inauguration address, considered one of the best inaugural speeches.

Obama's day on Sunday started with considerably more solemnity.

He went to Arlington National Cemetery - the country's hallowed burial ground for its war dead - and laid a wreath on the Tomb of the Unknown Soldier. Onlookers applauded as he passed by.

Later, the Obamas and Bidens attended church services separately.