President Joe Biden raised more than $15 million for his reelection campaign this past weekend from wealthy donors in the Los Angeles area, a source close to his campaign told AFP on Monday.

According to some press reports, a sitting president or presidential candidate has never before raised so much money in a single visit to the film metropolis, traditionally generous to Democratic candidates.

Biden held a series of fundraisers between Friday evening and Saturday evening.

While some meetings in mansions in the hills surrounding Los Angeles remained strictly confidential, journalists had access to two receptions designed to raise funds for the 81-year-old Democrat, who touted his record but above all launched a frontal attack on former president Donald Trump, his likely rival.

On Friday evening, in the airy courtyard of a villa, as filmmaker Steven Spielberg and others looked on, and before a private concert by Lenny Kravitz, Biden said Trump posed threats on many fronts.

"But the greatest threat Trump poses is to our democracy because if we lose that, we lose everything," Biden said.

"He embraces political violence instead of rejecting it. We can't let this happen," he added, referring to the possibility of a Republican victory in the presidential vote next autumn.

He renewed his warning the following day at another opulent residence, one valued at $50 million on the real estate market.

"After having stood as a beacon of freedom and equality for the entire world, I don't believe the 250th anniversary of this nation will turn to Donald Trump," he said, referring to the upcoming anniversary of the 1776 Declaration of Independence.

Biden has long been reluctant to even name his predecessor, whom he is likely to face again next November, much less attack head-on.

But Biden, chastened by sagging poll numbers and struggling to persuade voters of his economic policies, is resorting to a more direct approach.

The 2024 campaign promises to be the most expensive in US history, surpassing astronomical sums spent on past campaigns.

One eye-popping estimate says $16 billion may be spent on political advertising, mainly television and Internet, in the upcoming campaign, 30 percent more than in 2020. That is according to a forecast by the media agency GroupM, published by the Axios website.