The historic trial marks only the third such proceeding in US history. President Trump is charged with abuse of power and contempt of Congress.
The impeachment trial against President Donald Trump began in the US Senate on Thursday, starting with a reading of the charges.
John Roberts, the chief justice of the Supreme Court, was then sworn in to preside over the trial, which will determine whether Trump will be removed from office.
"All persons are commanded to keep silent, on pain of imprisonment, while the House of Representatives is exhibiting to the Senate of the United States articles of impeachment against Donald John Trump, President of the United States," the sergeant-at-arms announced.
The senators, who are acting as jurors, are not allowed to speak during the proceedings, and must submit any questions they have in writing.
What will happen?
After Roberts was sworn in, he administered an oath to deliver "impartial justice" to all 100 senators.
The two Democratic lawmakers from the House of Representatives leading the prosecution against Trump are Adam Schiff of California and Jerry Nadler of New York. The team of seven prosecutors also includes representatives from Texas, Colorado, and Florida.
After the charges were read and everyone sworn in, the proceedings were adjourned until Tuesday, as there are still administrative decisions to be made on how the trial will proceed.
It remained unclear whether the Senate's Republican majority would allow the calling of witnesses.
The trial could last weeks if witnesses testify. A two-thirds majority in favor of the prosecution is required for Trump's removal from office — a tall order in the Republican-controlled Senate.
What are the charges?
Trump has been charged with abuse of power and contempt of Congress. One charge relates to allegations that he withheld military aid to Ukraine as leverage to gain compromising information about Hunter Biden, the son of his Democratic rival Joe Biden, in addition to getting Ukrainian officials to investigate the conspiracy theory that hackers meddling in the 2016 US presidential election came from their country — and not Russia.
Trump was also charged with obstructing Congress' subsequent investigation. Documents and witness testimony from the probe revealed the likelihood that the president knew his personal lawyer Rudy Giuliani and the former New York City mayor's associate Lev Parnas were conducting a campaign to pressure the Ukrainian government into launching an investigation into the Bidens in exchange for the military aid.
Only former Presidents Andrew Johnson and Bill Clinton have been impeached in the US. President Richard Nixon resigned before the House could impeach him over the Watergate scandal.
Earlier on Thursday, the nonpartisan Government Accountability Office (GAO) announced that the White House budget office had broken the law by temporarily withholding the aid to Ukraine.
es/stb (AP, AFP)