A race by Democrats to remove President Donald Trump from office is gathering momentum as some of his fellow Republicans begin to break ranks.

The House of Representatives' third most senior Republican, Liz Cheney, said she would vote to impeach Mr Trump over last week's storming of Congress.

Earlier, the president took no responsibility for the riot, which resulted in five deaths.

He will be succeeded by Joe Biden, a Democrat, on 20 January.

The House plans to vote on Wednesday to charge Mr Trump with inciting insurrection, with Democrats saying the president encouraged his supporters to storm the Capitol building at a speech before the riot.

Mr Trump could become the first US president ever to be impeached twice. He became the third president to be impeached in December 2019 over charges of breaking the law by asking Ukraine to investigate Mr Biden in the election.

Ms Cheney, the daughter of former Vice-President Dick Cheney, vowed to back impeachment, the first time a leader of the president's own party has done so since Richard Nixon's time in office.

"There has never been a greater betrayal by a president of the United States of his office and his oath to the Constitution," the Wyoming representative said, adding that Mr Trump had "summoned this mob, assembled the mob, lit the flame of this attack".

Two other Republican House members, John Katko and Adam Kinzinger, said they would also vote for impeachment.

House Republican leader Kevin McCarthy, a Trump ally who has said he opposes impeachment, decided not to ask rank-and-file members of the party to vote against the measure, US media reported.

According to the New York Times, Senate Republican leader Mitch McConnell told confidants he was pleased Democrats wanted to impeach the president because he believed it would help rid the Republican party of Mr Trump.

On Tuesday evening, House Republican Brian Fitzpatrick of Pennsylvania introduced a resolution to censure Mr Trump, a congressional rebuke less severe than impeachment.

The measure accuses Mr Trump of "trying to unlawfully overturn" the results of November's election and of having "imperilled a coequal branch of Government".

The House passed a resolution by 223-205 votes on Tuesday calling on Vice-President Mike Pence to help oust Mr Trump using the 25th Amendment, which would allow the cabinet to remove the president if he is deemed unable to discharge his duties.

But Mr Pence had already rejected the Democrats' resolution, saying in a letter to House Speaker Nancy Pelosi: "Under our Constitution, the 25th Amendment is not a means of punishment or usurpation. Invoking the 25th Amendment in such a manner would set a terrible precedent."

Mr Pence's refusal to go along means that Democrats will proceed to an impeachment vote in the House. If Mr Trump is impeached, he would have a trial in the Senate to determine his guilt.

A two-thirds majority of the upper chamber would be needed to convict Mr Trump, meaning at least 17 Republicans would have to vote for conviction. As many as 20 Senate Republicans were open to convicting the president, the New York Times reported.

The Senate could also use an impeachment trial to hold a vote blocking Mr Trump, who has indicated he plans to campaign in 2024, from ever running for office again.

In his first public appearance since the riot, Mr Trump showed no contrition for remarks he made to supporters before the violence, when he also repeated unsubstantiated claims of voter fraud.

"What I said was totally appropriate," Mr Trump said. "I want no violence."

He also said: "This impeachment is causing tremendous anger, and you're doing it, and it's really a terrible thing that they're doing," adding that the "real problem" was rhetoric used by Democrats during Black Lives Matter protests and violence last year.

In the time it took Air Force One to fly Donald Trump back from the Texas border on Tuesday, the political ground crumbled beneath his feet. Mitch McConnell's signals that he is "pleased" with Democratic efforts suggest the political calculus is changing for Republican leaders in Congress.

A growing number believe the unrepentant president's actions last week threatened not just US democracy, but also their personal safety.

And even before the riot at the US Capitol, Mr Trump was increasingly viewed as a political liability with dwindling power. His scorched-earth challenge to the election results probably cost Republicans two Senate seats in Georgia, and there has been scant proof that Mr Trump boosts the party's electoral chances when his name is not on the ballot.

Mr McConnell, among others, may be mulling whether a clean break with Trump is better for their political futures, even if it means working with Democrats to do the job.

So far 170 individuals have been identified and 70 people charged, the FBI said. Hundreds more are expected to be charged and those found guilty of sedition and conspiracy could be facing up to 20 years in prison, the agency said.

Rioters are being urged to turn themselves into police while a social media campaign is ongoing by members of the public to identify people from photographs.

The FBI also said investigations had concluded that two pipe bombs found near political party offices in DC had explosive igniters and timers.

Meanwhile, US media reported that the day before the riots, the FBI issued an internal report warning that extremists were planning to travel to Washington DC to commit violence. The document, from an FBI office in Virginia, showed that plotters were sharing maps of the tunnels beneath the Capitol. (BBC)

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