US President Joe Biden has called Donald Trump a “convicted felon” who poses a higher threat to the US if he wins a second term.

Trump became the first US president to be convicted of a crime last week when a New York jury found him guilty of falsifying documents to cover up a payment to silence a porn star ahead of the 2016 election.

“For the first time in American history, a former president that is a convicted felon is now seeking the office of the presidency,” Biden told a small group of donors during a fundraiser in Greenwich, Connecticut on Monday (local time).

“But as disturbing as that is, more damaging is the all-out assault Donald Trump is making on the American system of justice,” he said.

The President’s comments offer a glimpse into how he and his campaign could use Trump’s conviction to make the case to voters Trump is unfit for office – an issue that could help define the presidential race by pushing Trump’s felonies to the centre of the election.

A Trump campaign spokeswoman said on Fox News it was “shameful” for the Biden campaign to call Trump a convicted felon. Trump said on Sunday he would accept home confinement or jail time after his historic conviction but that it would be tough for the public to accept.

At the Greenwich fundraiser, Biden also called Trump “unhinged” and unable to accept defeat. He stressed on Trump’s earlier comments about terminating the US Constitution and wanting to be a dictator on day one if he wins a second term.

“Throughout this campaign Trump has made it clear he is running to exact revenge. Now after his criminal convictions it’s clear he’s worried about preserving his freedoms,” Biden said.

Democrats are wrestling with how central Trump’s felonies should be to Biden’s re-election campaign. Many – including top officials in Biden’s campaign – are taking a wait-and-see approach to advertising and strategies and want to see polls and voter feedback before they react strongly to this unprecedented moment in US history.

A Reuters/Ipsos poll last week found 10 per cent of Republican voters said they were less likely to vote for Trump in November after his conviction.

Biden’s re-election campaign has told supporters that Trump can be beaten only at the ballot box, and has asked supporters for money.

Trump still faces criminal charges in three other cases: A Georgia election interference case, a Florida documents case and a federal election interference case. He is also appealing the results of his civil trials.

-AAP