House Speaker Nancy Pelosi signed two articles of impeachment against Donald Trump on Wednesday shortly before they were delivered to the Senate, where the US president faces trial on charges of abuse of power and obstruction of Congress.
"So sad, so tragic for our country, that the actions taken by the president to undermine our national security, to violate his oath of office and to jeopardise the security of our elections, has taken us to this place," Pelosi said shortly before using several ceremonial pens to sign the articles.
The articles were ceremonially walked through the US Capitol to the US Senate.
President Trump complained anew it was all a "hoax," even as fresh details emerged about his efforts in Ukraine.
Deeply divided nation
Earlier Wednesday, the House voted 228-193, almost entirely along party lines to deliver the charges.
The split reflected the deeply divided nation at the start of this presidential election year.
It came one month after the House impeached Trump alleging he abused his presidential power by pressuring Ukraine to investigate Democratic rival Joe Biden, using military aid to the country as leverage.
Trump was also charged with obstructing Congress' ensuing probe.
Trump's political campaign dismissed the House effort as "just a failed attempt to politically damage President Trump leading up to his reelection."
The Senate will transform itself into an impeachment court on Thursday.
The Constitution calls for Chief Justice John Roberts to preside at the trial, administering the oath to senators who will serve as jurors and swear to deliver "impartial justice."
Technically, the House was simply notifying the Senate of its delivery of the articles, with a more formal presentation Thursday. Opening arguments are to begin next Tuesday after the Martin Luther King Jr holiday.
The top Republican in the House, Kevin McCarthy of California, said Americans will look back on this "sad saga" that tried to remove the president from office with the "weakest case."
The president's team expects acquittal with a Senate trial lasting no more than two weeks, according to senior administration officials unauthorised to discuss the matter and granted anonymity.
That’s far shorter than the last presidential impeachment trial, of Bill Clinton, in 1999, or the first one, of Andrew Johnson, in 1868.