Rituals mark opening of Trump trial

The impeachment trial of US President Donald Trump on charges of abuse of power and obstruction of Congress began in the Senate on Thursday with a mixture of ritual and formalities and a solemn swearing-in of senators to do "impartial justice".

Only the third impeachment proceeding against a president in the country's history, it began with the reading aloud of the two articles of impeachment by Representative Adam Schiff of California, the Democratic-controlled House of Representative's lead impeachment manager. The senators sat silently under strict rules that prohibit talking or the use of cellphones.

During the trial, all senators will be warned by the sergeant at arms to remain silent "on pain of imprisonment" and will be expected to be present and seated at their assigned desks.

Two hours after Schiff got the opening proceedings under way, Supreme Court Chief Justice John Roberts, who will preside over the trial, was sworn in.

Ninety-nine of 100 senators were present for the swearing-in. Senator Jim Inhofe, a Republican from Oklahoma, was at home with a family member facing a medical issue, according to his office. He plans to be sworn in next week before the trial begins in earnest.

Aides said Trump wasn't watching the events on television. He told reporters in the Oval Office: "I think it should go very quickly. It's a hoax, it's a hoax. Everybody knows that."

Trial testimony won't get under way until the Senate reconvenes on Tuesday after the Martin Luther King Jr holiday weekend.

After the swearing-in, the Senate notified the White House of the pending trial and summoned Trump, but he will be given time to reply.

Senate Majority Leader Mitch McConnell, a Republican from Kentucky, recited unanimous agreements setting deadlines for trial documents. The House has until 5 pm on Saturday to file its trial brief, the White House until Monday noon to file its trial brief, and the House until noon on Tuesday to file its rebuttal.

At least two-thirds of the Republican-controlled Senate would have to vote to convict Trump to remove him from office. Trump has denied wrongdoing.

The articles accuse Trump of pressuring Ukraine President Volodymyr Zelensky to investigate a political rival, former US vice-president Joe Biden, while withholding a valuable White House meeting and $391 million in military aid. The withholding of the aid is central to the impeachment proceedings against Trump.

Shortly before the impeachment process got underway, the Government Accountability Office, or GAO, an independent congressional watchdog, said the Trump administration broke the law when it withheld the aid to Ukraine last year. The GAO said funds appropriated by Congress can't be withheld by the White House.

The White House criticized the decision as "overreach".

On Thursday, the White House also dismissed allegations from Lev Parnas, a businessman and former associate of Trump's personal attorney Rudy Giuliani, that Trump was aware of a scheme to get Ukraine to announce investigations into Biden, a potential Democratic rival in the 2020 presidential election.

Parnas turned over to House investigators what he said were details of a pressure campaign against Ukraine, and he said on Wednesday in an interview on CNN and with The New York Times that he believed Trump was fully aware of the efforts to dig up dirt on his political rival.

White House press secretary Stephanie Grisham attacked Parnas' credibility, accusing him of seeking attention on anti-Trump media outlets and pointing to Trump's denials that he knows the businessman, despite the two appearing in photos together. "We stand by exactly what we've been saying," she added. "The president did nothing wrong."