America crosses a risky crossroads as Biden becomes US president.

America leapfrogged a risky crossroads as Joe Biden was eventually sworn in as the 46th US president Wednesday, drawing the curtain on the most tumultuous administration of modern times and charting a new course to tackle Covid-19 and unite a splintered nation.

Outgoing President Donald Trump entered the White House four years ago as a brash billionaire outsider, but he is being ousted by a polar opposite whose deep knowledge of Washington and personal scars will unquestionably set a different tone.

Biden, a 78-year-old former vice president and longtime senator, took the oath of office at noon (1700 GMT) on the US Capitol's western front, the very spot where pro-Trump rioters clashed with police two weeks ago before storming Congress in a deadly insurrection.

While a transition of power occurs much as it has for more than two centuries, this inauguration is unlike any other.

Official Washington has taken on the dystopian look of an armed camp, protected by some 25,000 National Guard troops tasked with preventing any repeat of this month's attack.

And with the pandemic raging, the general public is essentially barred from attending the swearing-in ceremony, leading to the unprecedented sight of an empty National Mall on Inauguration Day.

With the death toll soaring past 400,000, Biden on Tuesday led a powerful tribute to victims of Covid-19 as he arrived in Washington.

Biden, who has suffered deep personal tragedy and is known for his public displays of emotion, has stressed the need to unite the country after Trump's chaos.

'It's hard sometimes to remember, but that's how we heal.

It's important to do that as a nation,' Biden said in somber remarks at the reflecting pool in front of the Lincoln Memorial.

- Trump snub - Inauguration eve is normally a time of massive crowds gathering in the capital, but Biden, joined by Vice President-elect Kamala Harris, was almost alone at the reflecting pool.

On the Mall's grassy expanse, some 200,000 flags have been planted to represent the absent crowds at the inauguration.

Trump, who has not appeared in public for a week, broke days of silence with a pre-recorded farewell video address on Tuesday.

For the first time, he asked Americans to 'pray' for the success of the incoming administration - a change from months spent persuading his Republican followers that the Democrats cheated their way to election victory.

Trump, whose efforts to combat the Covid- 19 pandemic and console its victims have been...