Watch: President Trump's impeachment trial kicks off in the Senate

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The Senate is scheduled to start paying 100% attention to the impeachment trial of President Donald Trump on Tuesday, the same day he touted his economic achievements to the World Economic Forum in Davos, Switzerland.

The House impeachment inquiry was triggered by Trump's July 25 phone call with Ukrainian President Volodymyr Zelenskiy. In the call, Trump pressed his counterpart to announce an investigation into Democratic rivals while withholding congressionally approved military aid.

A top government watchdog said Thursday that the Trump administration broke the law by withholding that military aid to Ukraine last summer "for a policy reason."

The report from the Government Accountability Office came a day after House Speaker Nancy Pelosi authorized the transmission of the articles of impeachment to the Senate.

Pelosi refused for weeks to move the articles to the upper chamber in an effort to force Senate Majority Leader Mitch McConnell to agree to terms for what she has called a fair process that would include new witnesses.

She announced impeachment managers last week, nearly a month after the president had been formally impeached by the House on Dec. 18 on abuse of power and obstruction of Congress charges.

McConnell has rebuffed Democrats' pleas to guarantee new witnesses, laying out rules that give each side 24 hours over two days to present their arguments in the trial, according to NBC News, which obtained a copy of McConnell's rules proposal Monday morning.

The rules also state that none of the evidence the House collected during the impeachment inquiry will be admitted automatically, according to NBC. Instead the Senate will vote on whether to admit any documents during the trial. The Senate will also be able to vote on whether to allow witnesses.

Chief Justice John Roberts, who will preside over the trial, was sworn in on Thursday, along with the senators, who will act as jurors.

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