Biden to face media in effort to quell age concerns

US President Joe Biden will try to head off growing opposition within his own party by sending out his advisers to meet with Democratic senators to shore up their support and holding his first solo news conference in almost eight months.

Biden's re-election campaign has been on the ropes for two weeks, since the 81-year-old incumbent's stumbling debate performance against Donald Trump, his 78-year-old Republican rival, raised fresh questions about his age and mental acuity - concerns that voters had long raised in public opinion polls.

The past week has brought a steady drip of elected Democrats calling on Biden to end his campaign, citing concerns that he could not only lose the White House but cost the party control of both chambers of Congress.

Peter Welch on Wednesday evening become the first Democratic US senator to call on Biden to step aside, joining at least nine Democratic members of the House of Representatives who have appealed to the president to withdraw from the race.

Welch, a first-term senator from Vermont, said Biden should end his candidacy "for the good of the country".

Democratic US senator Peter Welch
Peter Welch is the first Democratic US senator to call on President Joe Biden to step aside. (AP PHOTO)

Several high-profile lawmakers have said Biden should stay in the race, and many others, including former House Speaker Nancy Pelosi, have declined to say definitively whether he should step aside.

They will all likely be watching closely at 6.30pm eastern time on Thursday (8.30am on Friday AEST), when Biden is due to field questions from the White House press corps.

It had initially been slated for 5.30pm but the White House moved the time to an hour later.

At his first formal solo news conference since November 2023, Biden will have to speak extemporaneously on a wide range of topics, including likely questions on whether his doctors have found evidence of mental decline.

A White House official said it was expected to have a similar format to Biden's last solo news conference, when the president called on four reporters who asked about topics from defending Taiwan to deaths in Gaza and then answered a smattering of questions shouted at him.

Biden might call on a few more reporters this time, according to a person briefed on the matter.

His offhand reference to Chinese President Xi Jinping as a "dictator" at the end of the news conference capped a carefully-planned summit with Xi, and drew an angry response from China.

George Clooney
Actor George Clooney is among the high-profile Democratic donors opposing President Joe Biden. (AP PHOTO)

It will be Biden's most unscripted appearance since the June 27 debate, where he appeared to lose his train of thought several times and stumbled over several answers.

An interview with ABC News last week raised further alarms when Biden said he would be satisfied if he lost the election as long as he tried his best.

Before the news conference, several top aides, including Biden campaign chair Jen O'Malley Dillon, will meet Democratic senators at lunch in an effort to shore up support in the chamber where he served between 1973 and 2009.

A Reuters/Ipsos poll released last week found Biden and Trump tied at 40% each. Other opinion polls have found Trump widening his lead over Biden.

Biden has seen his fundraising advantage over Trump disappear in recent months, and some high-profile Democratic donors, including actor George Clooney, are calling on him to step aside.

Biden has insisted that he is not dropping out, and party rules make it all but impossible for anyone else to win the nomination at the Democratic National Convention in August unless he steps aside.

Democrats would also have to figure out how to hand the nomination to Vice President Kamala Harris or give others like Michigan Governor Gretchen Whitmer and Transportation Secretary Pete Buttigieg a chance to make their case.