WASHINGTON -- U.S. President Donald Trump was impeached by the U.S. House of Representatives, becoming only the third American chief executive to be formally charged under the Constitution's ultimate remedy for high crimes and misdemeanours.

The historic vote split along party lines Wednesday night, much the way it has divided the nation, over a charge that the 45th president abused the power of his office by enlisting a foreign government to investigate a political rival ahead of the 2020 election. The House then approved a second charge, that he obstructed Congress in its investigation.

The articles of impeachment, the political equivalent of an indictment, now go to the Senate for trial. If Trump is acquitted by the Republican-led chamber, as expected, he still would have to run for reelection carrying the enduring stain of impeachment on his purposely disruptive presidency.

"The president is impeached," Pelosi declared after the vote. She called it "great day for the Constitution of the United States, a sad one for America that the president's reckless activities necessitated us having to introduce articles of impeachment."

Trump, who began Wednesday tweeting his anger at the proceedings, pumped his fist before an evening rally in Battle Creek, Michigan, boasting of "tremendous support" in the Republican Party and saying, "By the way it doesn't feel like I'm being impeached."

The votes for impeachment were 230-197-1 on the first charge, 229-198-1 on the second.

Democrats led Wednesday night's voting, framed in what many said was their duty to protect the Constitution and uphold the nation's system of checks and balances. Republicans stood by their party's leader, who has frequently tested the bounds of civic norms. Trump called the whole affair a "witch hunt," a "hoax" and a "sham," and sometimes all three.

The trial is expected to begin in January in the Senate, where a vote of two-thirds is necessary for conviction. While Democrats had the majority in the House to impeach Trump, Republicans control the Senate and few if any are expected to diverge from plans to acquit the president ahead of early state election-year primary voting.

Pelosi, once reluctant to lead Democrats into a partisan impeachment, gaveled both votes closed, risking her majority and speakership to follow the effort to its House conclusion.

No Republicans voted for impeachment, and Democrats had only slight defections on their side. Voting was conducted manually with ballots, to mark the moment.

On the first article, abuse of power, two Democrats, Jeff Van Drew of New Jersey, who is considering switching parties to become a Republican, and Collin Peterson of Minnesota voted against impeaching Trump. On the second article, obstruction, those two and freshman Rep. Jared Golden of Maine voted against. Democratic Rep. Tulsi Gabbard of Hawaii, who is running for president, voted "present" on both.

What Pelosi called a sad and solemn moment for the country, coming in the first year after Democrats swept control of the House, unfolded in a caustic daylong session that showcased the nation's divisions.

The House impeachment resolution laid out in stark terms the articles of impeachment against Trump stemming from his July phone call when he asked the Ukrainian president for a "favour" -- to announce he was investigating Democrats including potential 2020 rival Joe Biden.

At the time, Zelenskiy, new to politics and government, was seeking a coveted White House visit to show backing from the U.S. as he confronted a hostile Russia at his border. He was also counting on $391 million in military aid already approved by Congress. The White House delayed the funds, but Trump eventually released the money once Congress intervened.

Narrow in scope but broad in its charges, the impeachment resolution said the president "betrayed the nation by abusing his high office to enlist a foreign power in corrupting democratic elections," and then obstructing Congress' oversight like "no president" in U.S. history.

"President Trump, by such conduct, has demonstrated that he will remain a threat to national security and the Constitution if allowed to remain in office," it said.

Republicans argued that Democrats were impeaching Trump because they can't beat him in 2020.

Said Rep. Chris Stewart of Utah: "They want to take away my vote and throw it in the trash."

But Democrats warned the country cannot wait for the next election to decide whether Trump should remain in office because he has shown a pattern of behaviour, particularly toward Russia, and will try to corrupt U.S. elections again.

"The president and his men plot on," said Chairman Adam Schiff, D-Calif., of the Intelligence Committee that led the inquiry. "The danger persists. The risk is real."

The outcome brings the Trump presidency to a milestone moment that has been building almost from the time the New York businessman-turned-reality-TV host unexpectedly won the White House in 2016 amid questions about Russian interference in the U.S. election.

Democrats drew from history, the founders and their own experiences, as minorities, women and some immigrants to the U.S. spoke of seeking to honour their oath of office to uphold the Constitution. Rep. Lou Correa of California spoke in Spanish asking God to unite the nation. "In America," said Hakeem Jeffries of New York, "no one is above the law."

Republicans aired Trump-style grievances about what Arizona Rep. Debbie Lesko called a "rigged" process.

"We face this horror because of this map," said Rep. Clay Higgins of Alabama before a poster of red and blue states. "They call this Republican map flyover country, they call us deplorables, they fear our faith, they fear our strength, they fear our unity, they fear our vote, and they fear our president."

The political fallout from the vote will reverberate across an already polarized country with divergent views of Trump's July phone call when he asked Zelenskiy to investigate Democrats in the 2016 election, Biden and Biden's son Hunter, who worked on the board of a gas company in Ukraine while his father was the vice-president.

Trump has repeatedly implored Americans to read the transcript of the call he said was "perfect." But the facts it revealed, and those in an anonymous whistleblower's complaint that sparked the probe, are largely undisputed.

More than a dozen current and former White House officials and diplomats testified for hours in impeachment hearings. The open and closed sessions under oath revealed what one called the "irregular channel" of foreign policy run by Trump's personal lawyer Rudy Giuliani, which focused on investigating the Bidens and alternative theories of 2016 election interference.

The question for lawmakers was whether the revelations amounted to impeachable offences.

Few lawmakers crossed party lines.

Van Drew, who is considering changing parties over his opposition to impeachment, sat with Republicans. Rep. Justin Amash, the Michigan conservative who left the Republican party and became an independent over impeachment, said: "I come to this floor, not as a Republican, not as a Democrat, but as an American."

Beyond the impeachments of Andrew Johnson and Bill Clinton, this first impeachment of the 21st century is as much about what the president might do in the future as what he did in the past. The investigation of Richard Nixon ended when he resigned rather than face the House vote over Watergate.

Rank and file Democrats said they were willing to lose their jobs to protect the democracy from Trump. Some newly elected freshmen remained in the chamber for hours during the debate.

Top Republicans, including Rep. Devin Nunes on the Intelligence Committee, called the Ukraine probe little more than a poor sequel to special counsel Robert Mueller's investigation of Russian interference in the 2016 election.

Mueller spent two years investigating the potential links between Moscow and the Trump campaign but testified in July that his team could not establish that Trump conspired or co-ordinated with Russia to throw the election. Mueller did say he could not exonerate Trump of trying to obstruct the investigation, but he left that for Congress to decide.

The next day, Trump called Ukraine. Not quite four months later, a week before Christmas, Trump was impeached.

------

Associated Press writers Laurie Kellman, Matthew Daly, Alan Fram and Andrew Taylor contributed to this report.