Apple and Nvidia have each handed over $25 million for US President Donald Trump's planned White House ballroom, according to a Washington Post report on Thursday. 

Two more $25 million cheques came from the Adelson family, longtime backers of Trump and his Republican Party, and from billionaire Charles Ergen, co-founder of Dish Network, the report added.

The president's pet project has pulled in $333 million in private donations, while Trump himself is not on the list, according to the Post.

The Post reported that the "vast majority of the funds raised came from companies and wealthy individuals with interests before the federal government" and that half the total came from firms or executives with federal contracts under Trump's second term.

Federal contractors Lockheed Martin, Microsoft and Palantir each gave $10 million, the Post reported. The companies did not immediately respond to a request for comment. 

Nvidia said it was proud to donate to a nonpartisan trust that serves Americans. "As an American company, our support for the United States is paramount, and independent of any business interests." Apple declined to comment.

Reuters has not verified the report. The White House said it would not release information about the donors, who spokesman Davis Ingle said "represent a wide array of great American companies."

"The same critics who are alleging fake conflicts of interests would also complain if American taxpayers were footing the bill for these long-overdue renovations," Ingle told Reuters.

Trump initially said he and wealthy donors would cover the estimated $400 million. He later asked Congress for $1 billion for a bunker and security upgrades – and didn't get it.

Trump's opponents see the ballroom as part of a "power grab": a push to remake Washington with sweeping, unilateral changes they have challenged in court.