An increasingly embattled US President Joe Biden is hitting the campaign trail in the battleground state of Pennsylvania as House Democratic Leader Hakeem Jeffries meets with senior House Democrats to discuss his candidacy.
Biden, 81, facing growing calls from fellow Democrats to end his re-election campaign after a halting performance in a June 27 debate with Republican Donald Trump, 78, has vowed to stay in the race and win the November 5 presidential election.
The president is struggling to put down a slow-boil uprising among some congressional Democrats and some influential donors who fear he cannot defeat Trump in light of the debate.
A much-anticipated interview with US broadcaster ABC News did little to put those concerns to rest.
Biden kept a low profile on Saturday, attending a church service in his hometown of Wilmington, Delaware, accompanied only by his sister and key adviser, Valerie Biden Owens.
In Friday's interview, Biden said only the "Lord Almighty" could persuade him to drop out, dismissing the prospect that Democratic leaders could join forces to try to talk him into standing down.
He spoke with the national co-chairs of his campaign on Saturday, the White House said, without providing any details.
On Sunday, Biden will address a Black church service in northwest Philadelphia before travelling to the state capital, Harrisburg, for a community organising event with union members and local Democrats, his campaign said.
Pennsylvania is one of the half-dozen or so states that can swing Democratic or Republican, which are expected to determine the outcome of what has been a tight race.
He will be joined during the day by Pennsylvania Governor Josh Shapiro, Lieutenant Governor Austin Davis, US Senators Bob Casey and John Fetterman, Philadelphia Mayor Cherelle Parker and other elected and community leaders, it said.
The trip is part of a July voter outreach blitz by the Democratic Party that includes a $US50 million ($A74 million) paid media campaign aimed at events such as the Olympic Games and travel by Biden, his wife, Vice President Kamala Harris and her husband to every battleground state.
The campaign said it aims to have volunteers and staff knock on more than three million voters' doors in July and August.
It will be Biden's 10th visit to Pennsylvania during the 2024 election cycle.
Pressure from Congress seems likely to ramp up in the coming days as lawmakers return to Washington from a holiday recess, and donors mull their willingness to keep funding his campaign.
The political crisis is unfolding as Biden prepares to host dozens of world leaders at a high-stakes NATO summit in Washington and hold a rare solo news conference.
Five US lawmakers have called for Biden to end his re-election bid, including Representative Angie Craig of Minnesota, the first Democratic member of the House of Representatives from a battleground district, with others said poised to join in.
“Given what I saw and heard from the President during last week’s debate in Atlanta, coupled with the lack of a forceful response from the President himself following that debate, I do not believe that the President can effectively campaign and win against Donald Trump,” Craig, a top 2024 target of House Republican efforts, posted on X.
Two letters are circulating among House Democrats calling for Biden to step aside, House Democratic sources have said.
US Senator Mark Warner of Virginia was contacting some fellow Democratic senators to invite them to a possible meeting on Monday to discuss Biden's campaign.
Biden told reporters he had spoken with 20 congressional Democrats who urged him to stay on and did not know any senators ready to join Warner.
