Donald Trump became the first US president to face a lawsuit in the Senate, the second time he has been charged with corruption.
Mr Trump has been accused of inciting a mob that erupted in Congress last week. Five people were killed.
The trial is set to begin next Wednesday after the president leaves office.
If Mr. Trump is convicted, senators could vote to prevent him from running for office again.
The trial follows a vote in the House of Representatives on Wednesday, which formally accused the president of “inciting revolt” for his role in the riots.
The Republican president has denied responsibility for the violence. In a video released after the vote, he called on his supporters to remain calm without mentioning their impeachment.
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The FBI has warned of possible armed demonstrations in Washington, D.C., and the capitals of all 50 U.S. states, which have been inaugurated by Democrat Joe Biden as the new U.S. president.
What happens next?
The upper house of the US Congress, the Senate, will hold a hearing to determine the president’s guilt, but not during the remaining weeks of Mr. Trump’s term.
Republican Senate Leader Mitch McConnell said “there is no possibility that a fair or serious trial will take place in light of the” rules, procedures, and precedent of the Senate “in which trials involving presidents are conducted. ۔
Punishing Mr. Trump would require a two-thirds majority, meaning at least 17 Republicans would have to vote with Democrats in a 100-seat evenly distributed chamber.
The New York Times reported Tuesday that about 20 Republicans are ready to sentence the president. In a note to colleagues, Mr McConnell said he had not made a final decision on how to vote.
If Mr Trump is convicted, then senators could vote again to prevent him from running for re-election, which he has indicated he intends to do in 2024. ۔
Mr Trump was persuaded by the House to deal with Ukraine in 2019, but was acquitted by the Senate.