The White House official said Trump’s pledge is not meant as a reimbursement to the RNC, but that it does not preclude Trump from doing that at a later time or for increasing the amount available for his aides.
The official requested anonymity to discuss the president’s plans, first reported by Axios, because Trump is not prepared to make a formal announcement.
The arrangement drew immediate criticism from Walter Shaub, the former director of the U.S. Office of Government Ethics, who suggested on Twitter that it is rife with potential conflicts.
“A potential witness or target of an investigation (and boss of investigators) paying for legal fees of other potential witnesses or targets?” Shaub wrote.
The White House official said many issues remain to be resolved, including how the money will be accessed and who can request it. The White House's and campaign aides' legal costs are expected to balloon well beyond what Trump is putting forward.
Russian meddling — and other related issues — are being investigated by special counsel Robert S. Mueller III as well as House and Senate committees.
The RNC reported last month that it paid $100,000 to Trump's personal attorney John Dowd and $131,250 to Jay Sekulow, another member of his legal team.
The party is also covering the mounting legal costs for Donald Trump Jr., spending nearly $200,000 on lawyers who helped him prepare for testimony before the Senate Judiciary Committee. Those payments included more than $166,000 to attorney Alan Futerfas.
The RNC is using a pool of money stockpiled for election recounts and other legal matters to pay the costs of Trump and his son.
RNC officials concluded that it is permissible for the party to pay for the president's legal fees, according to a person familiar with the conversations. Separately, party and administration officials are working to determine whether executive branch staff members could have their legal fees defrayed by the RNC or private legal defense funds.
Matea Gold contributed to this story.