Republicans and Democrats clashed over calling witnesses and demanding White House documents on the first full day Tuesday of the historic impeachment trial of President Donald Trump.

House impeachment managers led by veteran prosecutor Adam Schiff used the opening debate over trial procedures to lay out on national television their case against the US leader, underscoring why they want the Senate to immediately issue subpoenas for new evidence and Trump aides to testify.

Senate majority leader Mitch McConnell
Senate Majority Leader Senator Mitch McConnell (pictured January 14, 2020) proposed impeachment trial rules calling for each side to have 24 hours over two days to present their arguments. Photo: AFP / Mandel NGAN

"We are ready. The House calls John Bolton. The House calls Mick Mulvaney. Let's get this trial started, shall we?" Schiff challenged Republicans.

"We are ready to present our case. We are ready to call our witnesses. The question is, will you let us?" he said.

Republican Senate leader Mitch McConnell bared his own political muscle, mobilizing his side's 53-47 majority in the body to slap down one after another Democratic efforts to change the trial procedures he reportedly crafted together with the White House to protect Trump.

US President Donald Trump
President Donald Trump has said the impeachment is a political witch hunt and a hoax. Photo: AFP / SAUL LOEB

"The basic structure we're proposing is just as eminently fair and even-handed," McConnell said.

But Schiff said that order of procedure "makes no sense" and was designed instead to ensure evidence is never heard and Trump is exculpated.

"It's completely backwards, trial before evidence," he said. "Most Americans don't believe there will be a fair trial."

US President Donald Trump arrives in Zurich
US President Donald Trump arrived at Zurich International Airport ahead of his scheduled speech to the World Economic Forum in Davos. Photo: AFP / JIM WATSON

Trump was impeached on December 18 by the House of Representatives, and formally charged on the floor of the Senate last week with abuse of power and obstruction of Congress.

Nancy Pelosi, Adam Schiff and Jerry Nadler
Speaker of the House Nancy Pelosi, flanked by Impeachment Managers Rep. Adam Schiff (R) and Rep. Jerry Nadler, leaves a press conference after announcing the impeachment managers on Capitol Hill January 15, 2020. Photo: AFP / OLIVIER DOULIERY

Only the third president in history to face trial for removal, he is accused of illicitly pressuring Ukraine to aid his 2020 reelection campaign, by asking Kiev to investigate his potential election rival Joe Biden.

The first day of debate focused on rules mapped out by McConnell for the trial: three eight-hour days of arguments by the Democratic impeachment managers, and three days again for Trump's legal defense team.

After that would be one day of questions from the 100 senators, who serve as the jury.

US impeachment
US impeachment: Trump on trial. Photo: AFP / Gal ROMA

Only then, according to McConnell's rules, would the body consider proposals to call witnesses and seek internal documents from the Trump administration.

Democrats, who want to hear from current and former top Trump aides, including White House Chief of Staff Mick Mulvaney and former national security advisor John Bolton, were hoping that at least four Republicans would break with their party at that time to support subpoenas.

But they fear that McConnell will use his solid majority to reject witness subpoenas and quickly move for a final verdict on the two articles of impeachment.

Democratic prosecutor accuses Senate chief
Democratic prosecutor accuses Senate chief of rigging Trump trial. Photo: Senate Pool /

"McConnell continues his iron grip on the Republican majority," said Democratic Senator Chris Coons outside the hearing.

"The Republican majority is still going to try to tear through this case in 10 days."

Even without control of the Senate, Schiff's prosecution team took advantage of the rules debate Tuesday to detail their case against Trump to the American public.

They played videos of US diplomats testifying late last year that Trump oversaw the months-long scheme to pressure Ukraine to help him politically damage Biden and the Democrats.

They also played a video of Trump himself saying last December that he would "love to have" witnesses like Mulvaney appear.

"I want them to testify, but I want them to testify in the Senate," he said at the time.

Trump's lawyers, led by Pat Cipollone and Jay Sekulow, appeared to struggle to rebut the Democrat charge, ceding much of their opportunity to defend Trump on television and arguing mostly that the House investigation had been unfair to the president.

Cipollone accused the Democrats of "phony political investigations," against Trump.

"They are trying to remove President Trump's name from the ballot and they can't prove their case," he said, with Trump seeking re-election in November.

Trump advisor Kellyanne Conway told Fox News that Democrats "have no case."

"The burden of proof always rests on the prosecutors' table... you prove the case," she said. "They want us all to focus on witnesses... they don't want you to focus on substance."

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