With eight days remaining in Donald Trump’s term, the House will vote on an article of impeachment accusing the Republican of inciting insurrection in a speech to his followers last week before a mob of them stormed the Capitol.
US Vice President Mike Pence has told House leaders he does not support invoking the 25th Amendment process to remove Donald Trump, all but guaranteeing an impeachment vote against the besieged president.
"With just eight days left in the President's term, you and the Democratic Caucus are demanding that the Cabinet and I invoke the 25th Amendment," Mr Pence wrote to House Speaker Nancy Pelosi, referring to the process that would declare Mr Trump unable to fulfill his duties and install himself as acting president for the remainder of the term.
"I do not believe that such a course of action is in the best interest of our nation or consistent with our Constitution," he said.
Democrats mobilised rapidly to begin the process to have Mr Trump removed after he encouraged his supporters last Wednesday to "march" to the US Capitol and "fight."
In a violent insurrection, the rioters stormed past outnumbered police, rampaged through and ransacked the building, and interrupted Congress as it was certifying Joe Biden's election victory.
Mr Pence, who was presiding over the vote, as well as Ms Pelosi and other politicians, were forced to take shelter. Five people died during the unrest including a US Capitol Police officer.
The House of Representatives on Tuesday delivered a stinging rebuke to Mr Trump anyway, voting almost entirely along party lines to call on Mr Pence to take action and remove the president.
Despite the letter, the House passed a resolution formally calling on Mr Pence to act. The final vote was 223-205 in favour.
Ms Pelosi quickly announced her managers for the process, and a House impeachment vote has been scheduled for roughly 3pm on Wednesday (local time).
At least four Republicans have said they will join Democrats in voting to impeach Mr Trump over the attack: Liz Cheney, the daughter of former Republican vice-president Dick Cheney, John Katko, Adam Kinzinger and Fred Upton.
In his letter, Mr Pence told Ms Pelosi her call for invoking the 25th Amendment was misplaced, saying it was designed to "address presidential incapacity or disability," not as a "means of punishment or usurpation."
He also pointed out that despite intense pressure from within his party to invalidate the electoral votes from swing states won by Mr Biden, he fulfilled his consitutional duty to certify the results.
"I will not now yield to efforts in the House of Representatives to play political games at a time so serious in the life of our nation," he wrote.
The New York Times reported that the Republican majority leader of the US Senate, Mitch McConnell, was said to be pleased about the Democratic impeachment push, suggesting Trump’s party was looking to move on from him after last week’s stunning attack on Congress.
Mr McConnell believes the impeachment effort will make it easier to purge Mr Trump from the party, the Times said.
Earlier on Tuesday, Mr Trump said the 25th Amendment was of "zero risk" to him.