Biden defends his 'mental acuity' and still rejects calls to retire

Moreover, Biden said he is not losing. "We knew it was going to be a tight race from the moment we announced," Biden said. "The polling data shows a lot of different things, but there's not a big gap between us. It's essentially a two-man race," he added.

According to an NBC News poll, Trump is ahead of Biden by 2 percentage points.

But the poll also revealed that more than 60% of Democrats said they would prefer someone else as a presidential candidate. Eighty per cent of all voters also said they were concerned about Biden's mental and physical abilities.

Biden added that it was 'a mistake' to say he wanted to put Trump in 'a bull's eye', but defended his rhetoric that his opponent is a threat to democracy. He also dismissed the idea that he fuelled the escalation of political violence in the US, shifting the blame onto Trump: 'I'm not the guy who said he wanted to be a dictator on the first day of his inauguration, or who refused to accept the outcome of the election.

The president said he had Trump after Saturday's assassination attempt, calling the conversation "very cordial". "I told him how concerned I was and wanted to make sure I knew how he was actually doing," he said.

At the moment, it appears that Biden will be officially nominated by fellow Democrats for a second term in a virtual ballot to be held in late July, despite calls for him to step aside.

Democrats and Republicans usually use national conventions to officially nominate each other's candidates, but Biden will be nominated weeks before his party convenes for the Democratic National Convention in Chicago on 19 August - a plan that was announced long before Biden's poor performance on 27 June. It is unclear exactly how the early process will work: many details will be worked out on 19 and 21 July, when the party's convention rules and credentials committees will meet, respectively.

The virtual early nomination was originally intended to address an Ohio law that could have excluded Biden from the state's ballot if he was not nominated by 7 August, before the convention in Chicago. However, on 2 June, Ohio Governor Mike DeWine signed a bill extending the deadline to 31 August, meaning that the official nomination at the Democratic convention would still comply with Ohio law. An online or virtual vote means there is no chance of a live battle at the Chicago convention that could embarrass Biden and throw the campaign into chaos.

Biden's campaign officials said they expect Saturday's attack on Republican rival Donald Trump will divert attention, lessening the pressure on Biden to step aside.

Should Biden resign after the official nomination, the 435 members of the Democratic convention committee will choose a new candidate in a special session.

Meanwhile, some House Democrats have rebelled against the National Committee's plan to advance Biden's nomination before the Chicago Convention. Axios reports this, citing a letter circulated among Dems on Capitol Hill in which they point out that there is "no legal justification" for anticipating the nomination. "We ask that you cancel any plans for a 'virtual appeal' and further refrain from any extraordinary procedure that could be perceived as limiting legitimate debate," the letter reads.