(This January 11 story corrects paragraph 13 to clarify that it was Section 4 of the 25th Amendment that has never been used)
By Richard Cowan and David Morgan
WASHINGTON (Reuters) - Democrats in the U.S. House of Representatives plan to impeach Donald Trump on Wednesday unless he steps down or is removed before then, after drawing up charges accusing him of inciting insurrection ahead of last week's siege of the Capitol.
House Majority Leader Steny Hoyer told his fellow Democrats the chamber would take up impeachment on Wednesday if Vice President Mike Pence does not invoke the U.S. Constitution's 25th Amendment to remove Trump from office, a House aide said.
Passage would make Trump, a Republican, the only U.S. president ever to be impeached twice.
An impeachment would prompt the Senate to hold a trial to decide whether to convict and remove him from office, although it is unlikely the proceeding would be completed before Trump's term expires in nine days.
A Senate conviction could also lead to Trump being barred from holding public office again, ending his potential 2024 presidential bid before it begins.
U.S. Representative Tom Reed, a moderate Republican, said in a New York Times opinion piece that he and some colleagues would introduce a censure resolution against Trump on Tuesday as an alternative to a "rushed" impeachment.
"Impeachment now, days before Mr. Trump's term ends, would be a grave error, diluting the meaning of that important constitutional provision forever," Reed wrote. He said Congress should also examine ways to bar Trump from ever holding public office again.
But a censure is unlikely to satisfy furious Democrats. House Speaker Nancy Pelosi told Democratic members on Monday during a conference call that a censure would be an "abdication of our responsibility," according to a source familiar with the call.
Thousands of Trump supporters stormed the seat of Congress last Wednesday, 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 occurred shortly after Trump urged supporters to march on the Capitol during a rally where he repeated false claims that the Nov. 3 election was "rigged" against him.
Democrats formally introduced an impeachment charge on Monday, accusing Trump of "incitement of insurrection."
"The President represents an imminent threat to our constitution, our country and the American people, and he must be removed from office immediately," Pelosi said.
Republicans blocked a parallel effort to immediately consider a resolution asking Pence to invoke the never-used Section 4 of the 25th Amendment to remove an unfit president.
The House is expected to vote on Tuesday evening on the resolution as Democrats seek to ramp up pressure on Pence and his fellow Republicans.
Pence advisers said he opposed invoking the 25th Amendment, which allows a vice president and the Cabinet to remove a president who is incapable of fulfilling his duties.
Trump acknowledged a new administration would take office on Jan. 20 in a video statement after the attack but has still not conceded that he lost the election.
He has not been seen in public since the riot, although he met with Pence on Monday for the first time since lambasting him for refusing to block the certification of Biden's victory.
House Republican leader Kevin McCarthy told his members on Monday that Trump had acknowledged some blame for the violence, and McCarthy said he agreed with the president's self-assessment, according to a House Republican aide.
Twitter and Facebook have suspended Trump's accounts, citing the risk of him inciting violence.
Washington remains on high alert ahead of Biden's inauguration, which had already been scaled back dramatically because of the raging COVID-19 pandemic.
The National Guard was authorized on Monday to send in up to 15,000 troops, and tourists were barred from the Washington Monument due to threats of more violence from Trump supporters.
The FBI has warned that armed protests are being planned in the U.S. and state capitals ahead of the inauguration, according to a federal law enforcement official.
Two members of the Capitol Police have been suspended in connection with last week's attack and 10 to 15 officers are under investigation, Democratic U.S. Representative Tim Ryan told an online news conference.
One suspended officer took a selfie with a protester, while another wore a Trump-supporting hat and started directing protesters around, said Ryan, who chairs a House subcommittee looking into how Capitol security was breached.
The lawmakers who drafted the impeachment charge say they have locked in the support of at least 214 of the chamber's 222 Democrats, indicating strong odds of passage.
Democratic Representative Diana DeGette said some Republicans had privately expressed support for impeachment.
House Democrats impeached Trump in December 2019 for pressuring Ukraine to investigate Biden, but the Republican-controlled Senate voted not to convict him.
Even if the House impeaches Trump again, the Senate is not scheduled to return to Washington until Jan. 19.
Senate Democratic leader Chuck Schumer has been exploring ways to call the chamber back into emergency session, a senior Democratic aide said, although Republican Majority Leader Mitch McConnell would have to consent.
An impeachment conviction needs a two-thirds majority, which would require at least 17 Republican votes. So far, only a handful of Republican lawmakers have publicly said they would consider voting for impeachment.
Other Republicans have urged Democrats to abandon impeachment in the name of unity.
Senator Joe Manchin, a moderate Democrat, called the impeachment drive "ill-advised" on Monday in a Fox News interview, saying he saw no path to a conviction in the Senate.
Democrats will take Senate control once the winners of Georgia's recent runoff elections are seated, which will create a 50-50 split with Vice President-elect Kamala Harris holding the tiebreaking vote after she and Biden take office.
Some Democrats worry an impeachment trial could tie up the Senate during Biden's first weeks in office, preventing the new president from installing Cabinet secretaries and acting on priorities like coronavirus relief.
Biden said on Monday he had spoken to some senators about whether they could oversee a trial and Senate business at the same time.
"Can you go a half day on dealing with the impeachment and a half day getting my people nominated and confirmed in the Senate as well as moving on the (stimulus) package? That's my hope and expectation," he told reporters in Delaware after getting his second dose of the coronavirus vaccine.
(Reporting by Richard Cowan and David Morgan; Additional reporting by Susan Cornwell, Doina Chiacu, Lisa Lambert, Andy Sullivan, Steve Holland, Mark Hosenball, Andrea Shalal and Jeff Mason; Writing by Joseph Ax and John Whitesides; Editing by Paul Simao, Rosalba O'Brien and Peter Cooney)