Biden campaigns in Pennsylvania, braces for defections

US President Joe Biden urged supporters to stay unified at a rousing Black church service in critical Pennsylvania, even as his campaign team quietly braced for growing pressure on him to abandon his re-election bid.

Speaking from a stage flanked by sunshine from stained-glass windows at northwest Philadelphia's Mount Airy Church of God in Christ, the 81-year-old Biden laughed off concerns about his age, joking: "I know I look 40" but "I've been doing this a long time".

"I, honest to God, have never been more optimistic about America's future if we stick together," Biden said, Sunday.

He didn't use a teleprompter, which has become more common since his disastrous debate performance, but spoke from a prepared speech.

That followed Biden joining a Saturday call with campaign surrogates and reiterating that he has no plans to leave the race, despite a political situation that is increasingly precarious.

Instead, the president pledged to campaign harder going forward and to hit the road more frequently, according to two people who spoke on condition of anonymity to discuss private conversations.

Five Democratic lawmakers have already called on him to abandon his re-election campaign ahead of November, and more could do so in the coming days, as Congress reconvenes.

Meeting in person means more chances to discuss concerns about Biden's ability to withstand the remaining four months of the campaign — not to mention four more years in the White House — and true prospects of beating former Republican former President Donald Trump.

Biden's campaign team is quietly preparing for more Democrats to say the president should yield to another candidate in coming days, while holding the call with surrogates and calling and texting lawmakers to try and head off more potential defections.

They are also tasking high-profile Biden supporters to speak out, in hopes of bringing those with lingering concerns back in line.

Alan Clendenin, a Tampa city councilman and member of the Democratic National Committee, said on Sunday: "I believe it is in the best interest of our country and the world that President Joe Biden step aside and allow Vice President Kamala Harris to carry forward his agenda as our Democratic nominee."

And director Rob Reiner, who has helped organise glitzy Hollywood fundraisers for Biden in the past, posted on X: "It's time for Joe Biden to step down".

With the Democratic convention fast approaching, the short term is especially critical.

Those who feel Biden is no longer up to the task are imploring Democrats to replace him at the top of the ticket before, they argue, it's too late.