Washington, Jan 22 (AFP) Democrats were to present opening arguments in the Senate impeachment trial of Donald Trump on Wednesday after a day of strict party line votes on ground rules that foreshadowed the president's likely acquittal.

Trump, who was attending the World Economic Forum in Davos as the historic trial got underway, blasted the proceedings as a "witchhunt" and a "hoax" and said he expected the Republican-majority Senate to clear him "fairly quickly."

Republicans, who hold a 53 to 47 seat edge in the Senate, shot down a series of bids by Democrats to introduce White House witnesses and documents on Tuesday during nearly 13 hours of acrimonious debate that lasted late into the night.

Trump defended the Republicans' rejection of Democratic efforts to force former national security advisor John Bolton and others to testify at his trial saying of Bolton, for example, that it would present a "national security problem".

"John, he knows some of my thoughts," Trump said. "He knows what I think about leaders. What happens if he reveals what I think about a certain leader and it's not very positive?"

The 100 members of the Senate were to be back at their desks -- sitting silently and without their cellphones -- at 1:00 pm (1800 GMT) as House prosecutors begin formally laying out their case that Trump should be removed from office for "high crimes and misdemeanors."

The seven members of the House of Representatives, which impeached Trump on December 18, will have 24 hours over the next three days to make their case that the 45th US president is guilty of abuse of power and obstruction of Congress.

White House lawyers will then have 24 hours to present their defense of Trump, who maintains he did nothing wrong by asking his Ukrainian counterpart to open an investigation into Democrat Joe Biden, his potential November election rival.

On Tuesday, House prosecutors and White House lawyers squared off in fiery exchanges over the rules for just the third impeachment trial in US history.

Democrats used the opportunity to spell out their arguments for Trump's guilt on national television.

They used detailed graphics and played videos of US diplomats testifying last year to demonstrate that Trump oversaw a months-long scheme to pressure Ukraine into helping him politically by damaging Biden.

"They don't want a fair trial," said Adam Schiff, the chief House prosecutor. "If the Senate votes to deprive itself of witnesses and documents, the opening statements will be the end of the trial."

Republican Senate leader Mitch McConnell slapped down all of the Democratic attempts to introduce witnesses and documents at the start of the trial, insisting the question be considered only later in the proceedings.

Democratic Senator Chuck Schumer lashed out at the majority leader on Wednesday.

"If there's one thing we learned here on the Senate floor it's that Leader McConnell and Senate Republicans don't want a fair trial that considers all the evidence," Schumer said.

After both sides present their cases, senators will have an opportunity to ask written questions to be read out aloud by US Supreme Court Chief Justice John Roberts, presiding over the trial.

Roberts' roles is mostly ceremonial but he did warn both sides, near the end of a marathon day marked by bitter clashes, to watch their decorum.

"I think it is appropriate at this point for me to admonish both the House managers and president's counsel in equal terms to remember that they are addressing the world's greatest deliberative body," Roberts said.

"Those addressing the Senate should remember where they are."

Trump's lawyers, led by Pat Cipollone and Jay Sekulow, appeared to struggle to rebut the Democratic attack on Tuesday, arguing mostly that the House investigation had been unfair to the president.

Cipollone accused the Democrats of "phony political investigations," against Trump ahead of his November re-election fight.

"They are trying to remove President Trump's name from the ballot and they can't prove their case," he said.

The next few days are likely to be an endurance test for members of the Senate, some of whom are in their 80s.

Barred from having their phones and computers at their desks, they scribbled on notepads, chatted quietly, fidgeted and stretched on Tuesday.

The four Democratic senators seeking to challenge Trump for the White House have been forced to take time off from campaigning ahead of the first state caucuses to choose their party's nominee in Iowa on February 3.

"We're all there to do our duty," said Minnesota Senator Amy Klobuchar, who is seeking the nomination along with Vermont Senator Bernie Sanders, Massachusetts Senator Elizabeth Warren and Colorado Senator Michael Bennet.

"I can do two things at one," Klobuchar said.

Little doubt remains about the outcome of the trial, given the Republicans' Senate majority and Trump's command of party loyalty.

A two-thirds majority, or 67 senators, is required to convict Trump and remove him from office. (AFP)

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