In a historic action , which has divided the nation and sent the political temperatures soaring, the US House of Representatives has passed two articles of impeachment against Trump.
Trump is facing charges of abuse of power and obstruction of Congress relating to his dealings with Ukraine and the House investigations into it.
The Republicans, who are outnumbered in the House, tried unsuccessfully to delay the proceedings when the House began its sitting by introducing motions that were voted down.
In a letter to Democrat Speaker Nancy Pelosi, Trump denounced the impeachment as an "unprecedented and unconstitutional abuse of power" and a witch hunt.
Pelosi wrote to her party Representatives to vote for impeachment in order to "defend our Constitution from all enemies, foreign and domestic".
Third President to be impeached in US:
Donald Trump is the third U.S. president to be impeached, after the House votes that he abused his power by pressuring Ukraine to investigate a political rival.
Only two Presidents - Andrew Johnson in 1868 and Bill Clinton in 1998 - have been impeached in the nation's 243-year history.
Charges against Trump:
Democrat Representative Jim McGovern said in the House on Wednesday that Trump was seeking foreign interference in the 2016 elections through his request to Ukraine President Volodymyr Zelensky to investigate former Vice President Joe Biden and his son Hunter over a business deal.
Another Democrat Lori Trahan said Trump used his position for personal and political gain by withholding military aid to Ukraine to pressure it to launch the probes and endangered national security.
Ro Khanna, a Democrat, accused Trump of corrupting national politics and contributing to the threat of national decline.
The impeachment follows up on the charges of foreign interference in the 2016 election by Russia that has been persistently made by Democrats since Hillary Clinton's defeat.
Foreign interference was the recurring theme of the speeches by Democratic Party Representatives who said Trump's request to Zelensky in a July 25 phone call to investigate a potential election rival in 2020 was an invitation to meddle in the election.
Biden's son was appointed to the board of directors of a Ukrainian gas company with monthly payments of $83,000 even though he had no energy business experience and had been removed from the navy because of alleged drug abuse.
The process ahead:
The impeachment process is only the framing of a charge sheet known as the Articles of Impeachment which will be sent to the Senate for a formal trial presided over by the Supreme Court Chief Justice to determine the fate of the President.
The two Articles of Impeachment against Trump are certain to be passed by the House Democratic majority, but the Republican-controlled Senate will not vote to convict Trump when it holds the trial next year.
Of the 233 House Democrats, at least two have announced that they will cross the divide and oppose the impeachment, while the 197 Republicans are standing by the President.
The two Democrats are from constituencies that voted for Trump and they feared that their constituents would vote against their re-election if they voted for impeachment.
The focus will now shift to the Senate where the Democrats will send representatives to act as prosecutors.
The Senate will have to decide on the procedure for the trial. Trump wants a full-fledged trial with several witnesses being called to testify, but Mitch McConnell, the Republican leader in the Senate, has said he wants a short, quick trial.
The procedure will have to be hashed out between them.
The Senate Democratic Party leader Chuck Schumer has demanded that former National Security Adviser John Bolton, Trump's Chief of Staff Mick Mulvaney and two other officials be called as witnesses in the Senate.
Republicans, who were not allowed by Democrats to call their witnesses in the House proceedings, have opposed Schumer's demand.