Washington: President Joe Biden has launched a new era in US politics, moving to rapidly dismantle some of his predecessor Donald Trump's signature policies while calling for Americans to end their "uncivil war" and rediscover a sense of common purpose.

Earlier, just hours after Trump departed the White House for a new life as a private citizen in Florida, Biden stood on the steps of the Capitol building to declare that democracy had prevailed in America.

Just a fortnight earlier, Trump supporters who rejected the outcome of the November election stormed the Capitol in a riot that shocked the world and led to five deaths.

Lady Gaga arrives to perform the National Anthem as Joe Biden and Kamala Harris watch on, outside the US Capitol which was invaded by Trump supporters a fortnight ago.Credit:AP.

Trump was the first outgoing president since 1869 not to attend his successor's inauguration, although Biden said that Trump had left him a gracious personal note in the White House.

"We will be back in some form," Trump told supporters at Joint Base Andrews in Maryland.

An estimated 25,000 National Guard troops had been stationed in Washington in the lead-up to the inauguration and entry to the ceremony was tightly restricted.

Pop star Lady Gaga performed the national anthem at the inauguration ceremony while country music singer Garth Brooks sang Amazing Grace