Congressional Democrats began a push on Monday to force U.S. President Donald Trump from office.
They introduced one article of impeachment accusing him of inciting insurrection over a violent attack on the Capitol last week.
The Democratic-controlled House of Representatives is expected to take up the matter as early as Wednesday. Passage would make Trump, a Republican, the only president in U.S. history to be impeached twice.
Thousands of Trump supporters stormed the Capitol last week, forcing lawmakers who were certifying Democratic President-elect Joe Biden's election victory into hiding in a harrowing assault on the heart of American democracy that left five dead.
The violence came after Trump urged supporters to march on the Capitol at a rally where he repeated false claims that his resounding defeat in the November 3 election was illegitimate.
House Speaker Nancy Pelosi, many of her fellow Democrats and a handful of Republicans say the Republican president should not be trusted to serve out his term, which ends on January 20.
"In protecting our Constitution and our Democracy, we will act with urgency, because this President represents an imminent threat to both," Pelosi wrote to her fellow House Democrats on Sunday.
Earlier, Republicans blocked an effort to immediately consider a resolution asking Vice President Mike Pence to invoke the U.S. Constitution's never-used 25th Amendment to remove an unfit president.
The House is expected on Tuesday to vote on the resolution calling for use of the 25th Amendment, which allows the vice president and the Cabinet to remove a president who is incapable of fulfilling his duties.
Pence and his fellow Republicans have shown little interest in invoking the amendment.
Dozens of people who attacked police officers, stole computers and smashed windows at the Capitol have been arrested for their role in the violence, and officials have opened 25 domestic terrorism investigations.
Trump acknowledged that a new administration would take office on January 20 in a video statement after the attack but has not appeared in public.
Twitter and Facebook have suspended his accounts, citing the risk of him inciting violence.
Even if the House impeaches Trump again, the Senate, which is currently controlled by Republicans, would not take up the charges until January 19 at the earliest, Trump's last full day in office.