Washington  - America and the world's eyes turned Tuesday to the US capital for the inauguration of Barack Obama as the country's first African-American president.

Obama was to be sworn in as president just before noon on the steps of the US Capitol building in Washington, in front of a record crowd that could reach 2 million people by some estimates.

Obama enters the White House carrying the sky-high expectations of both Americans and the rest of the world. He faces an economic downturn that could be the worst since the Great Depression as well as ongoing wars in Iraq and Afghanistan.

In his inaugural speech Tuesday, Obama was expected to strike a delicate balance between the realities of the challenges ahead and and the optimistic tone that helped him the November 4 elections.

Obama, 47, has sought to play down expectations in recent weeks, warning that the economy will likely "get worse before it gets better" and urging all US citizens to do their part to turn around the country's fortunes.

He reinforced that message on Monday, rolling up his sleeves and joining other Americans in observing the birthday of slain civil- rights leader Martin Luther King Jr with a nationwide call to community service.

More than 5,000 volunteer groups helped organize 11,000 community projects, involving as many as 1 million participants across the country, Obama said.

"We're gonna have to take responsibility, all of us," Obama said in a stop at Calvin Coolidge High School in Washington. "If we're just waiting around for somebody else to do something, it never gets done."

For African-Americans, Obama's inauguration is a huge step toward fulfilling hopes of racial equality that King evoked in his famous "I Have A Dream" speech in 1963.

The opportunity to witness history has brought millions of people from across the country to Washington to witness Obama's inauguration as the 44th president, filling hotel rooms as far as 400 kilometres from the city.

Supporters prepared for long lines, tight security and freezing temperatures to watch him take the oath of office. Huge crowds were already roaming Monday on the National Mall, a vast, park-like expanse that extends from the Capitol to the Lincoln Memorial.

Long lines of ticket recipients for the inauguration waited outside congressional offices on Capitol Hill to collect their passes. People crowded into nearby subway entrances for 20-minute waits just to get onto the platform.

"Because of the nature of this man, the potential of his presidency, people are prepared to be patient and put up with things they'd never put up with under ordinary circumstances," said Sharon Kanter, 68, of Kinston, North Carolina, who was lucky enough to snag a ticket for Tuesday.

A total of 240,000 tickets for seating and close-in standing areas for the swearing-in ceremony were distributed, mostly via congressional offices. Potentially millions more spectators without tickets will be able to watch - albeit at great distances - along the length of the mall, which has been lined with huge video screens.

On Wednesday, his first full day in office, Obama plans to meet with his economic advisers and military commanders as he works to quickly implement new policies in both areas.

Obama may immediately issue a series of executive orders reversing some of Bush's decisions, including a possible directive to close the controversial detention facility for suspected terrorists on the US naval base at Guantanamo Bay, Cuba. (dpa)