The US Senate has acquitted Donald Trump of inciting the mob that stormed the Capitol last month, sparing him from conviction in his second impeachment trial in a year despite broad condemnation of his role in sparking the deadly siege.
The Senate voted 57-43 in favour of convicting the former president, falling short of the two-thirds majority needed, on a charge he incited the insurrection that left five people dead, forced lawmakers to flee and put his own vice-president in danger while overseeing the certification of Democrat Joe Biden's election win.
Senate Republican Leader Mitch McConnell, who voted "not guilty" in the trial, offered scathing remarks about Trump after the verdict.
"There is no question that President Trump is practically and morally responsible for provoking the events of the day," he said on Saturday. "The people who stormed this building believed they were acting on the wishes and instructions of their president."
In the vote, seven of the 50 Senate Republicans joined the chamber's Democrats in favouring conviction after a week-long trial in the same building ransacked by Trump's followers after they heard him deliver an incendiary speech on January 6.
During the trial, senators viewed graphic video of the assault, including scenes of the mob chanting "hang Mike Pence" as it hunted the vice-president.
Trump left office on January 20, so impeachment could not be used to remove him from power. But Democrats had hoped to hold him responsible for the siege and set the stage for a vote to stop him serving in public office again.
"The bottom line is that we convinced a big majority in the Senate of our case," said Representative Jamie Raskin, the lead Democratic prosecutor from the House of Representatives.
House Speaker Nancy Pelosi said Republicans' refusal to hold Trump accountable would be remembered "as one of the darkest days and most dishonourable acts in our nation's history".
The swift end to the trial allows Biden to move forward with his agenda to bolster the economy with a $US1.9 trillion ($A2.4 trillion) pandemic relief bill and further confirmation of his cabinet members.
But divisions on Capitol Hill and around the country over his controversial predecessor will remain.
"This has been yet another phase of the greatest witch hunt in the history of our country," Trump said in a statement after his acquittal.
Trump, 74, continues to hold a grip on his party with a right-wing populist appeal. The businessman-turned-politician has considered running for president again in 2024.
Republicans saved Trump in the February 5, 2020, vote in his first impeachment trial, when only one senator from their ranks - Mitt Romney - voted to convict and remove him from office.
Romney voted for conviction on Saturday along with fellow Republicans Richard Burr, Bill Cassidy, Susan Collins, Ben Sasse, Pat Toomey and Lisa Murkowski.
Trump is only the third president to be impeached by the House as well as the first to be impeached twice and the first to face an impeachment trial after leaving office.
The House approved the article of impeachment against Trump on January 13, with 10 Republicans joining the chamber's Democratic majority, a week after the Capitol siege.
Shortly before the rampage, Trump urged his followers to march on the Capitol, repeated his false claims that the election was stolen from him through widespread voting fraud, and told them "if you don't fight like hell, you're not going to have a country any more".
During the trial, nine House lawmakers serving as trial managers urged senators to hold Trump accountable for a crime against American democracy and to prevent a repeat.
The defence lawyers accused Democrats of trying to silence Trump as a political opponent and attempting to criminalise political speech with which they disagreed.
Trump could still face other congressional action against him such as a censure motion, but Pelosi said such a measure would let Republicans who voted against conviction "off the hook".
McConnell suggested Trump might be prosecuted for his acts. "He didn't get away with anything. Yet," McConnell said.