White House lawyers say voters should decide Trump's fate

White House lawyers began their defense of Donald Trump at his historic Senate impeachment trial on Saturday, saying the president did nothing wrong in his dealings with Ukraine and American voters - not Congress - should decide his fate.

White House counsel Pat Cipollone said it would be a "completely irresponsible abuse of power" if the Senate follows the lead of the House of Representatives and votes to remove the 45th US president from office. "They're asking you to do something that no Senate has ever done," Cipollone told the 100 senators gathered on a rainy Saturday morning for a rare weekend session at just the third impeachment trial in US history.

Democratic prosecutors from the House, which impeached Trump last month for abuse of power and obstruction of Congress, had not convincingly made their case that the president had committed "high crimes and misdemeanors," as demanded by the Constitution, Cipollone said.

"We don't believe that they have come anywhere close to meeting their burden for what they're asking you to do," he told a hushed Senate chamber. "We believe when you hear the facts... you will find that the president did absolutely nothing wrong."

House prosecutors spent the previous three days laying out a detailed case that Trump withheld military aid to Ukraine and a White House meeting to pressure his Ukrainian counterpart to open an investigation into political rival Joe Biden and the former vice president's son Hunter, who served on the board of a Ukrainian gas company.

Adam Schiff, the chief House prosecutor, said the real estate tycoon turned politician poses an "imminent threat" to American democracy and his guiding principle is "Trump first, not America first."

Cipollone argued that Democrats were asking the Senate to "tear up all of the ballots" from the 2016 presidential election and attempting to prevent Trump from running for re-election in November.

"They are here to perpetrate the most massive interference in an election in American history and we can't allow that to happen," the White House counsel said. "Let the people decide for themselves."

The Democratic-controlled House impeached Trump on December 18 in a party-line vote, setting up a trial in the Senate, where Republicans hold a 53 to 47 seat edge and the president enjoys the support of Majority Leader Mitch McConnell.

A two-thirds majority, or 67 senators, is required to remove a president from office and Democrats do not appear to have made any significant inroads so far in Trump's wall of Republican support.

Following the session, top Senate Democrat Chuck Schumer said the president's attorneys "made a really compelling case" for calling witnesses during the trial, a move Trump has opposed.

Senator Mitt Romney, a Republican from Utah and occasional Trump critic, said he was "likely" to support the Democrats' demand but other Republicans indicated that their minds were all but made up.

"Today we heard a case that was strong, that was clear and that completely undermined the case of the Democrats," Senator John Barrasso, a Republican from Wyoming, said of the White House defense.

Just before his lawyers began speaking, Trump fired off a tweet with insulting nicknames for leading Democrats and told his supporters to tune in to the live television broadcast.

The White House lawyers kept their opening arguments short - just under two hours - in part, perhaps, because Trump, a former reality television star, had complained that Saturday is the "Death Valley" of TV viewership.

Following the defense presentation, Trump claimed it had demonstrated how "unfairly" he has been treated and showed he was the victim of a "partisan Impeachment Hoax."

Trump's lawyers will resume his defense on Monday. They will have 24 hours spread over three days for their arguments but have said they are unlikely to use all the time allotted.

Saturday's brief session was a relief to the four senators battling for the Democratic presidential nomination, allowing them to return to the campaign trail.

Vermont Senator Bernie Sanders, Massachusetts Senator Elizabeth Warren, Minnesota Senator Amy Klobuchar and Colorado Senator Michael Bennet have been forced to remain in Washington while Biden and other candidates campaign in Iowa, which kicks off the nominating process on February 3.

Senators will have 16 hours next week to direct questions to both sides and consider whether they should subpoena witnesses, something Democrats have sought but Republicans have opposed.

The questions from senators will be submitted in writing to US Supreme Court Chief Justice John Roberts, who is presiding over the trial and will read them out loud.

Americans appear about evenly split on whether Trump should be removed, though several polls show a healthy majority want the Senate to subpoena witnesses for Trump's trial.