WASHINGTON Billionaire Mike Bloomberg has given nearly US$20 million to help Democratic President Joe Biden's re-election effort against Republican former president Donald Trump, two sources familiar with the matter told Reuters on Thursday.

Bloomberg's contribution included US$19 million to an independent pro-Biden group known as Future Forward or FF PAC, and over US$900,000 to the Biden Victory Fund, which is an amalgamation of the Biden campaign and Democratic Party committees, the sources added, asking not to be identified.

The donations were first reported by The Washington Post. The Biden campaign did not immediately respond to a request for comment.

Bloomberg, the former New York mayor who spent US$1 billion of his own money on a failed 2020 presidential bid in the Democratic primaries, injected at least US$100 million to help Biden's campaign against Trump in Florida in 2020. Trump, who lost the overall 2020 race to Biden, had won in Florida by over three percentage points.

Biden and Trump have mostly been tied in national polls.

Democrats have maintained an overall cash advantage over Trump and the Biden campaign continues to have a considerably larger war chest. Biden's campaign reported US$84 million in the bank at the end of April, compared with US$49 million reported by Trump.

However, Biden campaign's fundraising in April lagged Trump's for the first time, after the former president ramped up his joint operation with the Republican National Committee and headlined high-dollar fundraisers.

Pro-Trump spending groups have spent more than US$25 million since Trump clinched the Republican nomination on March 6, Federal Election Commission records show, compared to more than US$15 million spent by Biden's allies during the same time.

  - Reuters