Biden slams US Supreme Court at star-studded fundraiser

The US Supreme Court is "out of kilter", President Joe Biden has told a glitzy fundraiser in Los Angeles with former president Barack Obama and top Hollywood celebrities that raised $US28 million ($A42 million).

Late-night TV host Jimmy Kimmel began by showing a video montage contrasting Biden's record with that of his predecessor and current Republican challenger Donald Trump.

He drew cheers from the audience at a packed Peacock Theatre in downtown Los Angeles, where Hollywood celebrities George Clooney and Julia Roberts were among the guests.

Biden, a Democrat who has frequently denounced specific decisions but resisted a full-throated attack on the court itself, said on Saturday "the Supreme Court has never been as out of kilter as it is today".

"There has never been a court that is this far out of step," Biden said.

He noted that conservative Justice Clarence Thomas had said the court, which overturned the half-century-old federal right to abortion, should reconsider such things as in-vitro fertilisation and contraception.

Trump nominated three of the six conservatives who control the nine-member court.

He and Biden are in a tight rematch race for the November 5 election.

If Trump is elected again, Biden said, he "is likely to have two new Supreme Court nominees".

"The idea that if he's re-elected he's going to appoint two more who are flying flags upside down ... I think it is one of the scariest parts," Biden said.

He was referring to a recent controversy involving Justice Samuel Alito, who allowed flags associated with the movement to reverse Trump's 2020 loss to Biden - including an upside-down American flag - to fly outside his homes in Virginia and New Jersey.

Democratic lawmakers, citing the flag displays, have said Alito should recuse himself from a case involving Trump's claim of presidential immunity from prosecution on federal criminal charges relating to his efforts to overturn the 2020 results.

Since Biden took office, the court's conservative majority has also restricted affirmative action, gay rights, gun control and environmental regulation.

It has blocked the president's agenda on immigration, student loans, vaccine mandates and climate change.

Obama said "the power of the Supreme Court is determined by elections".

"What we're seeing now is a by-product of 2016" when Trump was elected, he said.

"Hopefully we have learned our lesson - because these elections matter," Obama said.

The Biden campaign hoped the star-studded event would display strength and momentum despite Biden's low approval ratings and concerns about the age of the president, who is 81.

A Biden campaign spokeswoman said "$US28 million ($A42 million) heading into President Biden's LA fundraiser - and counting".

"This is the largest Democratic fundraiser in history," she said.

The top-ticket package for the LA event cost $US500,000 ($A757,000), campaign officials said.

Other celebrities who took the stage at the Saturday event included Jack Black, Jason Bateman, Kathryn Hahn and Sheryl Lee Ralph.

In recent weeks, Mark Hamill of Star Wars fame made a White House briefing room appearance to praise the president, Robert De Niro showed up in lower Manhattan for a press conference at the Biden campaign's behest and Steven Spielberg has been helping the Biden campaign with storytelling.

Actor Michael Douglas held a fundraiser for the president and artists Queen Latifah, Lenny Kravitz, Lizzo, James Taylor, Christina Aguilera and Barbra Streisand have all performed to help Biden raise money.

Biden and Trump are tied in national polls with less than five months to go before the election, while Trump has the edge in the battleground states that will decide the election, recent polls show.

On economic issues such as inflation, Trump scores higher with voters overall than Biden.