A RASPY and sometimes halting US President Joe Biden tried repeatedly to confront Donald Trump in their first debate ahead of the November election.

But the Republican rival countered Mr Biden’s criticism by leaning into falsehoods about the economy, illegal immigration and his role in the January 2021 Capitol insurrection.

Mr Biden’s terrible performance, particularly early in the debate, crystallised the concerns of many US citizens that, at 81, he is too old to serve as president.

It sparked a fresh round of calls for the Democrat to consider stepping aside as the party's nominee, as members of his party fear a return of Mr Trump to the White House.

Mr Biden repeatedly tore into Mr Trump in an apparent effort to provoke him, bringing up everything from the former president’s recent felony conviction, to his alleged insult of World War I veterans, to his weight.

The 78-year-old Trump declined to clearly state he would accept the results of the November election, four years after he promoted conspiracy theories about his loss that culminated in the insurrection, and repeatedly misstated the record from his time in office.

But Mr Biden’s delivery from the beginning of the debate drew the most attention afterward. Mr Trump’s allies immediately declared victory while prominent Democrats publicly questioned whether Mr Biden could move forward.