‘I promise you we are going to win this election,’ Biden tells Democrat donors

US President Joe Biden has assured Democrat donors that he can still win November's presidential election against Donald Trump, after a poor debate performance fuelled concern about his candidacy.

The president, 81, attended a series of fundraising events in New York and New Jersey on Saturday, and defended his performance in CNN's Presidential Debate.

Speaking at one event, Biden admitted: "I didn’t have a great night, but neither did Trump”.

"I promise you we're going to win this election," he said.

Biden's debate performance was marked by hard-to-follow and shaky answers - raising fresh fears among some Democrats over whether he is the right candidate to contest this high-stakes election.

Former Democratic House speaker Nancy Pelosi said Biden's debate performance “wasn’t great” - while his former communications director, Kate Bedingfield, called it “really disappointing”.

The US President said he understood the concern, but pledged to fight harder.

New Jersey's Democratic governor Phil Murphy attended the fundraiser alongside Biden and the First Lady - and told Biden that "we are all with you 1,000%".

The Biden campaign accepted that the debate had not gone as they had hoped, but said he would not step aside for another nominee.

Former President Barack Obama, a close friend of Biden, said on social media that "bad debate nights happen".

"This election is still a choice between someone who fought for ordinary folks his entire life and someone who only cares about himself," Obama wrote.

Hours after the debate, Donald Trump told his supporters that he considered the debate a "big victory" for his campaign.

"Joe Biden's problem is not his age," the 78-year-old Trump said. "It's his competence. He's grossly incompetent."