* Trump assails "Do Nothing" Democrats, vows: "We will win!"
* Pelosi says Republicans have "taken an oath" to Trump
* House panel could approve impeachment charges by Dec. 12
* Inquiry taking place among deep partisan divisions (Adds comment from Town Hall, paragraph 10)
By David Morgan, Susan Cornwell and Richard Cowan
WASHINGTON, Dec 5 (Reuters) - Warning that U.S. democracy is at stake, House of Representatives Speaker Nancy Pelosi directed a congressional committee on Thursday to draft articles of impeachment against President Donald Trump, a historic step setting up a fight over whether to oust him from office.
In a dramatic televised statement, Pelosi accused the Republican president of abusing his power and alluded to Britain's King George III, the monarch against whom the American colonies rebelled in forming the United States in 1776, saying that in the United States, "the people are the king."
"Our democracy is what is at stake. The president leaves us no choice but to act because he is trying to corrupt, once again, the election for his own benefit. The president has engaged in abuse of power, undermining our national security and jeopardizing the integrity of our elections," said Pelosi, the top Democrat in Congress.
At the heart of the Democratic-led House's impeachment inquiry is Trump's request that Ukraine launch an investigation targeting Joe Biden. The former vice president is a top contender for the Democratic nomination to face Trump in the 2020 presidential election.
"Sadly, but with confidence and humility, with allegiance to our founders and our heart full of love for America, today I am asking our chairman to proceed with articles of impeachment," Pelosi said. She had opened the investigation in September.
She was referring to Jerrold Nadler, whose House Judiciary Committee has the responsibility of drawing up the formal charges that would later be voted on by the full House.
Two people knowledgeable about the process said the panel could draft and recommend the articles of impeachment to the House as early as Dec. 12. Democrats said lawmakers would work through the weekend to get them written.
The charges could include abuse of power, bribery, obstruction of Congress and obstruction of justice.
If articles of impeachment are passed as expected, that would lead to a trial in the Senate. Republicans, who control the Senate, have shown little support for convicting and removing him.
Pelosi was asked what it would take for Republicans to support impeachment as she took questions at a Town Hall on CNN on Thursday night. "I can't answer for the Republicans, they've taken an oath to Donald Trump," she answered.
Trump, who has denied wrongdoing, wrote on Twitter: "The Do Nothing, Radical Left Democrats have just announced that they are going to seek to Impeach me over NOTHING."
"The good thing is that the Republicans have NEVER been more united. We will win!" Trump said.
Pelosi's announcement clearly signaled that she believes Democrats have the votes in the 435-seat House to impeach. She acted after receiving overwhelming support in a party meeting on Wednesday night, a source familiar with the meeting said.
The impeachment drama is unfolding at a time of deep partisan divisions across the United States that have widened during Trump's tumultuous presidency.
The inquiry's focus is a July 25 telephone call in which Trump asked Ukrainian President Volodymyr Zelenskiy to open an investigation into Biden and his son Hunter, and a discredited theory promoted by Trump and his allies that Ukraine, not Russia, meddled in the 2016 U.S. election.
Hunter Biden had joined the board of Ukrainian energy company Burisma while his father was vice president. Trump has accused the Bidens of corruption. They have denied wrongdoing and the allegations have not been substantiated.
Democrats have accused Trump of abusing his power by withholding $391 million in security aid to Ukraine - a vulnerable U.S. ally facing Russian aggression - as leverage to pressure Kiev into conducting investigations politically beneficial to Trump.
Republicans accuse Democrats of trying to overturn the results of the 2016 election. They have described Trump's actions as aimed at weeding out corruption in Ukraine, not getting political dirt on Biden.
They also argue the inquiry has failed to produce first-hand evidence showing Trump made U.S. aid to Ukraine or a White House meeting for its president contingent on Kiev pursuing the investigations.
On Wednesday, the Judiciary Committee held a hearing in which three constitutional law experts called by Democratic lawmakers said Trump had committed impeachable offenses. A fourth expert called by Republicans called the inquiry slipshod and rushed.
Nadler has given Trump until 5 p.m. (2200 GMT) on Friday to say whether he or his legal counsel will participate in upcoming proceedings by calling witnesses, introducing evidence and making a presentation. Nadler has given committee Republicans the same deadline to request witnesses.
Judiciary Democrats said the report by former Special Counsel Robert Mueller documenting Russian interference in the 2016 election could be part of testimony they hear on Monday from a committee lawyer, who is presenting evidence along with a Democratic lawyer from the House Intelligence Committee. Republican committee lawyers are also expected to testify.
Including material from Mueller's report in an article of impeachment would demonstrate a pattern of behavior involving foreign interference in U.S. elections, House Judiciary Democrat Pramila Jayapal said.
"What we have to think about is what gives us the strongest trial in the Senate," she told reporters.
The U.S. Constitution empowers the House to impeach a president for "treason, bribery or other high crimes and misdemeanors."
No U.S. president has ever been removed from office through impeachment. Republican Richard Nixon resigned in 1974 after the House began the process in the Watergate corruption scandal.
Two other presidents were impeached by the House but acquitted by the Senate.
In 1998, a Republican-led House passed articles of impeachment against Democratic President Bill Clinton, charges arising from a sexual relationship he had with a White House intern. The other president impeached by the House but left in office by the Senate was Andrew Johnson in 1868, three years after the U.S. Civil War.
Asked if he worried that impeachment would tarnish his legacy, Trump told reporters at the White House: "No, not at all, not at all. It's a hoax, it's a big fat hoax."
(Reporting by David Morgan, Susan Cornwell and Richard Cowan; Additional reporting by Susan Heavey, Jeff Mason, Tim Ahmann, Lisa Lambert and Patricia Zengerle; Writing by Paul Simao, Sonya Hepinstall and Patricia Zengerle; Editing by Will Dunham and Peter Cooney)
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