Joe Biden has been sworn in as the US President with a call for unity after four years of chaos and rancour under Donald Trump.
He and his vice-president, Kamala Harris, who is the first woman to hold the post, took the oath of office amid security concerns following deadly riots by Trump supporters in Capitol Hill this month.
Addressing the deep divisions in American society, he called for an end to this "uncivil war".
Trump dodged the inauguration.
The event, which was marked by social distancing due to the pandemic, featured singer Lady Gaga singing the American national anthem and a performance by Jennifer Lopez.
With his hand on an heirloom Bible that has been in his family for more than a century, Biden took the presidential oath of office administered by U.S. Chief Justice John Roberts, vowing to "preserve, protect and defend the Constitution of the United States."
During his speech, the new President said political extremism and white supremacy had to be challenged. He added that he would put his "whole soul" in putting the UK back together.
"At this hour, my friends, democracy has prevailed," he said. "Today we celebrate the triumph, not of a candidate, but of a cause. The cause of democracy."
Speaking ahead of the inauguration, Senator Amy Klobuchar said the siege on the Capitol two weeks ago ''awakened us to our responsibility as US citizens''.
