US president-elect Joe Biden has said Donald Trump isn’t “fit for the job” of president, but he has repeatedly refused to endorse growing Democratic calls to impeach him a second time.

US house speaker Nancy Pelosi said in a letter to members of her chamber that legislators could move as early as next week to impeach Mr Trump for inciting a violent mob that overran the US Capitol if the president did not “immediately” resign.

Ms Pelosi and Democratic senate leader Chuck Schumer also have called on US vice president Mike Pence and the cabinet to invoke the 25th Amendment to force Mr Trump from office – a process for stripping the president of his post and installing the vice president in his place.

Addressing reporters in his home state of Delaware after an event on Friday to introduce some of his cabinet choices, Mr Biden noted that a key reason he ran for president was because he had “thought for a long, long time that President Trump wasn’t fit for the job”.

Mr Biden added: “I’ve been saying for now, well, over a year, he’s not fit to serve.

“He’s one of the most incompetent presidents in the history of the United States of America.”

But the president-elect refused to back efforts to remove Mr Trump from the White House and insisted that impeachment was up to the US congress.

Instead, Mr Biden said he was focused on the start of his own administration on January 20, and he said his top three priorities are beating back the coronavirus, distributing vaccines fairly and equitably, and reviving the struggling economy.

His comments laid bare the political balance Mr Biden has worked to strike in the months since winning the presidential election.

US Capitol
Preparations take place for President-elect Joe Biden’s inauguration on the West Front of the US Capitol in Washington (AP)

He has continued to sharply criticise Mr Trump and nearly every facet of his administration but also worked to keep the public’s attention focused on what the new administration will do, rather than indulging recriminations against the last one.

Mr Biden nonetheless conceded that Mr Trump “exceeded my worst notions about him. He’s been an embarrassment”, and likened the “damage done to our reputation around the world” to “tin horn dictatorships”.

The president-elect also suggested that a key hurdle to removing Mr Trump was that he has less than two weeks remaining in his term.

“If we were six months out, we should be doing everything to get him out of office. Impeaching him again, trying to evoke the 25th Amendment, whatever it took,” Mr Biden said.

“But I am focused now on us taking control as president and vice president on the 20th and to get our agenda moving as quickly as we can.”

Mr Trump would be the only president to be impeached twice. The house of representatives impeached him in late 2019, but the Republican-led senate acquitted him.

Removal from office could also prevent Mr Trump from running for president in 2024, or ever holding the presidency again.

Most Democrats, and many Republicans, put the blame squarely on Mr Trump after hundreds of rioters broke into the Capitol on Wednesday and caused destruction and mass evacuations.

The president had urged his supporters to protest as congress was counting the electoral votes that confirmed Mr Biden’s win. Five people died, including a Capitol Police officer.

Mr Biden called what happened a “god-awful debacle” and said it had “the active encouragement of the president of the United States”.

The president-elect’s comments came hours after Mr Trump tweeted that he planned to skip Mr Biden’s inauguration, becoming the first president in more than 150 years – and just the fourth in US history – to do so.

Mr Biden said he would be “honoured” to have Mr Pence at the swearing-in, but did not feel the same way about Trump.

That is “one of the few things he and I have ever agreed on,” Mr Biden said. “It’s a good thing, him not showing up.”

Also Friday, Mr Biden called on the senate – which will be under narrow Democratic control thanks to a pair of run-off election victories in Georgia – to confirm his cabinet choices “promptly and fairly”.

“Given what our country’s been through the last few days,” Mr Biden said, “they should be confirmed as close to January 20 as possible.”