US President Donald Trump is set to miss the swearing-in of his successor Democrat Joe Biden, he has confirmed on Twitter. One source says he'll leave office a day earlier, flying to his Florida resort.

Outgoing US President Donald Trump said Friday that he will not be attending President-elect Joe Biden's inauguration on January 20. 

"To all of those who have asked, I will not be going to the Inauguration on January 20th," he wrote on Twitter.

To all of those who have asked, I will not be going to the Inauguration on January 20th.

— Donald J. Trump (@realDonaldTrump) January 8, 2021

The decision appeared to backtrack on a message Trump gave a day earlier that he would work to ensure a "smooth, orderly and seamless transition of power" to his Democrat Party successor in the wake of the US Capitol riotson Wednesday.

Reuters news agency cited a source in the Trump administration as saying that the outgoing president would likely leave the White House a day before the inauguration and head to his Florida resort.

Impeachment debate

The announcement came as some lawmakers in Congress were to debate whether to bring articles of impeachment to the House of Representatives for a vote after pro-Trump rioters stormed the US Capitol building.

Wednesday's violence saw his supporters occupy the building for several hours as lawmakers were tallying the electoral votes that certified Biden's victory. The riotous incident left five people dead.

Trump was accused of inciting the crowd, gathered for a speech near the White House, to march on the Capitol, then refused to forcefully condemn the violent assault for at least a day and appeared to excuse it.

House Speaker Nancy Pelosi discussed the prospect of impeachment with her leadership team Thursday night.

Hours earlier, she said the House of Representatives was willing to act if Vice President Mike Pence did not invoke Section 4 of the 25th Amendment of the US Constitution — which permits the forceful removal of a president from power by his own Cabinet.

On Friday, Pelosi said she had also spoken to the chairman of the Joint Chiefs of Staff about preventing Trump from launching a nuclear strike during his final days in office.

In a letter to her colleagues, Pelosi said she wanted to prevent him from "initiating military hostilities or accessing the launch codes."

"The situation of this unhinged President could not be more dangerous," she warned.

Pence will attend

Despite Trump's absence, Pence is still expected to attend the swearing-in event.

Trump's move had been widely expected, as for weeks he falsely claimed victory in the US presidential election and promulgated baseless claims of voter fraud.

His own administration said the election had been fairly run.

Trump will be the first incumbent president since Andrew Johnson to skip his successor's swearing-in. 

Traditionally, the incoming and outgoing presidents ride to the US Capitol together for the ceremony, as a symbol of the nation's peaceful transition.