"We're never gonna be able to raise dollar for dollar with Biden," a Trump campaign adviser said in a call with reporters.

The adviser blamed the fundraising disparity on "billionaire" supporters of the Democratic president, and appeared keen to paint a picture of a Trump campaign fueled by grassroots, working-class supporters.

A second campaign adviser said Trump's campaign is "fueled by hundreds of thousands of grassroots contributors across the country, and I'd much rather have that because each one of those votes."

Asked for a response, Biden campaign spokesperson Ammar Moussa said: "Trump's campaign is strapped for cash."

Democratic candidates have raised more money in support of their White House bids than their Republican counterparts in all election cycles after 2004. Money, however is not always an indication of success; Trump beat Democratic candidate Hillary Clinton in 2016 even though she raised far more cash than he did.

Biden has been routinely outraising former President Trump, whose campaign, together with a joint fundraising committee, pulled in $20.3 million in February compared with the more than $53 million raised by Biden's reelection effort that month.

Large contributions make up about 55% of the $128.7 million that Biden's campaign committee has raised so far in the election cycle, OpenSecrets data showed, compared with 45% from small contributions.

For Trump, large contributions comprise 64% of the $96.1 million his campaign committee has raised, versus 36% from small contributions.

The two face a Nov. 5 general election rematch, in a race that opinion polls suggest will be extremely close.

Biden was holding a star-studded fundraiser in New York on Thursday night with his Democratic predecessors Barack Obama and Bill Clinton that his campaign said has already raised $25 million.

The Trump campaign is due to hold a fundraiser on April 6 hosted by billionaire hedge fund manager John Paulson in south Florida that aims to bring in $33 million, according to a person familiar with the event.

The Trump advisers on Thursday said that together with the Republican National Committee, the campaign will be opening dozens of offices and hiring hundreds of staff in the next few weeks, as they ramp up their general election infrastructure now that Trump has become the Republican Party's presidential candidate.

Trump cemented his grip over the RNC in March when a loyalist, his daughter-in-law, and a senior campaign adviser were installed as chair, co-chair and chief of staff of the organization following his endorsement. An aggressive overhaul ensued, with dozens of employees losing their jobs.

As part of the leadership restructuring, a new slate of deputies will focus on battleground states as well as relationships with state parties and grassroots organizations, the second Trump campaign adviser said. Gone are regional directors who oversaw broad areas of the country.

"Folks that are focused on the battleground states will have a very narrow focus," the adviser said. "We will not have that sort of middle layer that has historically existed to oversee a large region."