Trump acknowledges Biden will be next US President in wake of deadly Capitol chaos

As the threat of a second impeachment loomed, President Donald Trump acknowledged on Thursday that Joe Biden will be the next US President, a day after his supporters stormed the Capitol in a stunning assault on American democracy as Congress was certifying Biden's victory.

Trump, who as recently as Thursday morning had continued to claim falsely that the election had been stolen from him, said his focus would now turn to ensure a smooth transition to a Biden administration in a video released on Thursday evening.

Biden, a Democrat, is set to be sworn in on January 20.

The President condemned Wednesday's violence, saying rioters had defiled the seat of American democracy.

"Serving as your President has been the honour of my lifetime," Trump, a Republican, said.

"And to all of my wonderful supporters, I know you are disappointed, but I also want you to know that our incredible journey is only just beginning."

The statement was a stark reversal for Trump, who faced growing calls for his resignation or ouster following Wednesday's assault.

Trump has spent months insisting he prevailed in the November 3 election due to widespread fraud, despite no evidence.

His exhortation on Wednesday to thousands of supporters that they march to the Capitol to protest the election results whipped up a mob that overran police officers and invaded the Capitol building, forcing members of Congress into hiding for their own safety.

The top Democrats in Congress, House of Representatives Speaker Nancy Pelosi and Senate Democratic leader Chuck Schumer, called on Vice President Mike Pence and Trump's Cabinet to use the U.S. Constitution to remove Trump for "his incitement of insurrection."

The 25th Amendment allows a majority of the Cabinet to remove a president from power if he is unable to discharge the duties of the office.

But a Pence adviser said the vice president, who would have to lead any such effort, was opposed to using the amendment to oust Trump from the White House.

If Pence fails to act, Pelosi signalled she would likely reconvene the House to initiate impeachment proceedings against Trump for his role in Wednesday's violence, which claimed five lives, including that of a Capitol Police officer, whose death was confirmed on Twitter by U.S. Representative Dean Phillips.

A handful of Republicans also called for Trump's removal. The Wall Street Journal editorial page, seen as a leading voice of the Republican establishment, called on Trump to resign on Thursday evening.

Several members of Trump's administration, including Elaine Chao, the transportation secretary and the wife of Senate Majority Leader Mitch McConnell, resigned as a symbolic gesture against the violence.

(Reporting by Steve Holland and Andrea Shalal; Additional reporting by Matt Spetalnick, David Shepardson, Michael Martina, Lisa Lambert, Susan Heavey, Daphne Psaledakis, Doina Chiacu, Susan Cornwell, Richard Cowan, Jan Wolfe, Trevor Hunnicutt and Jonathan Landay; Writing by Joseph Ax and Andy Sullivan; Editing by Will Dunham, Howard Goller and Peter Cooney)