Washington, Jan 16 (AP) The Senate opens its historic proceedings against President Donald Trump on Thursday with a formal reading of the articles of impeachment by House prosecutors, followed by the arrival at the Capitol of Chief Justice John Roberts, who will swear in all 100 senators as jurors for only the third impeachment trial in US history.

The chamber begins to transform itself into an impeachment court at noon following a second day of ceremonial protocol that shifts the proceedings out of Speaker Nancy Pelosi's Democratic-run House to the Republican-majority Senate.

The House lawmakers prosecuting the case will read the charges to the Senate, then, later in the day, Roberts will administer the jurors' oath to senators who swear to deliver “impartial justice.” The events, unfolding during an election year as Trump seeks another term, will be a test not only of his presidency but also of the nation's three branches of power and its system of checks and balances. Several senators are running for the Democratic party's nomination to challenge Trump in November.

The president calls the impeachment a “hoax," even as new information emerges about his actions toward Ukraine that led to the charges against him.

Pelosi said new allegations from an indicted associate of Trump lawyer Rudy Giuliani, Lev Parnas, only reinforces the need for the Senate to consider further testimony about the president's actions toward Ukraine.

Pelosi noted that typically a special prosecutor would investigate but she doubted that would happen.

"This is an example of all of the president's henchmen,” Pelosi said, "and I hope that the senators do not become part of the president's henchmen.” Trump faces a charge that 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.Ahead of the proceedings the Government Accountability office said Thursday that the White House violated federal law in withholding the security assistance to Ukraine, which shares a border with hostile Russia.

Senate Majority Leader Mitch McConnell opened the chamber Thursday decrying Pelosi's decision to hand out "souvenir pens” after she signed the resolution to transmit the charges to the Senate.

“This final display neatly distilled the House's entire partisan process into one perfect visual,” McConnell said. “'It was a transparently partisan process from beginning to end.” Democratic Senate leader Chuck Schumer renewed his party's request that the trial include new witnesses and documents not available for the House impeachment proceedings.

“What is the president hiding? What is he afraid of?'' Schumer said.

“The gravity of these charges is self-evident," he said. “The House of Representatives have accused the president of trying to shake down a foreign leader for personal gain.” The president has suggested recently that he would be open to a quick vote to simply dismiss the charges, but sufficient Republican support is lacking for that. Still, an eventual vote to acquit Trump is considered highly likely.

On Wednesday, in a dramatic procession across the U.S. Capitol, House Democrats carried the charges to the Senate.

“Today we will make history,'' Pelosi said as she signed the documents, using multiple pens to hand out and mark the moment. “This president will be held accountable." Moments later the prosecutors walked solemnly through the stately hall, filing into the Senate back row as the clerk of the House announced the arrival: “The House has passed House Resolution 798, a resolution appointing and authorizing managers of the impeachment trial of Donald John Trump, president of United States.”

Opening arguments are to begin next Tuesday after the Martin Luther King Jr. holiday. Earlier Wednesday, the House voted 228-193, almost entirely along party lines, ending a weeks-long delay to deliver the charges with a tally reflecting the nation's split.

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. That would be far shorter than the trial of President Bill Clinton, in 1999, or the first one, of President Andrew Johnson, in 1868. Both were acquitted.

The seven-member prosecution team is led by the chairmen of the House impeachment proceedings, Reps. Adam Schiff of the Intelligence Committee and Jerrold Nadler of the Judiciary Committee, two of Pelosi's top lieutenants. (AP)

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