WASHINGTON (AP):

IN A private White House ceremony yesterday, Barack Obama swore for a second time to "protect and defend" the United States Constitution, officially affirming the duties of president in an oath he will repeat for hundreds of thousands of people during gala ceremonies today.

The day of festivities, parades, and fancy-dress balls will mark the beginning of Obama's second four-year term as America's first black president. The politician, who rose improbably from a history as a community organiser in Chicago and a professor of constitutional law to the pinnacle of power, faces a nation riven by partisan disunity, a still-weak economy, and an array of challenges abroad.

Obama will today take the oath again before the crowd and is expected to follow the recent tradition of walking at least part of the way back to the White House, surrounded by cheers.

Intimate swearing-in

In the briefest of ceremonies yesterday, with family gathered in the White House, Obama took the oath of office shortly before noon, as required by law. With his left hand on a family Bible held by First Lady Michelle Obama, the 44th president raised his right hand and repeated the time-honoured words read out by Supreme Court Chief Justice John Roberts.

The intimate swearing-in met the legal requirement that presidents officially take office on January 20. Because that date fell on a Sunday this year, the traditional public ceremonies surrounding the start of a president's term were put off to Monday, which coincides this year with the birthday of revered civil rights leader Martin Luther King.

Obama made no special remarks at yesterday's ceremony.

"I did it," he said quietly to his younger daughter, Sasha, before wrapping her in a hug. The oath went smoothly, unlike four years ago when Roberts made mistakes while trying to recite the oath from memory and had to do it again with Obama later.

Monday's events are expected to have less of the effervescence of four years ago when the 1.8 million people who packed into central Washington knew they were witnessing history. Obama is now older, grayer, and more entrenched in the politics he once tried to rise above. Officials are expecting 500,000 to 700,000 people to turn out today.