Donald Trump has rubbished a report alleging he made a promise to a foreign leader, something that sparked a whistleblower’s formal complaint.
The Washington Post said the intelligence official found the comment “so troubling” they went to the department’s inspector general.
In a tweet, Mr Trump dismissed the claims as “fake news”.
Democrats are trying to get the complaint turned over to Congress, with the details still unknown.
It is not yet known who made the complaint, which foreign leader Mr Trump was speaking to, what promise – if any – was made and whether Mr Trump took any action as a result.
Intelligence Community Inspector General Michael Atkinson, said the complaint consists of a “serious or flagrant problem, abuse or violation of the law” that involves classified information, a letter to lawmakers revealed.
The complaint was filed on 12 August, while Mr Trump was at his golf resort in New Jersey, according to the Post, which noted five foreign leaders with whom Mr Trump had interactions in the preceding five weeks.
During that time he phoned Russia’s Vladimir Putin, received at least two letters from North Korean dictator Kim Jong Un, and met at the White House with the leaders of Pakistan, the Netherlands and Qatar.
In his tweet Mr Trump wrote “is anybody dumb enough to believe that I would say something inappropriate with a foreign leader”.
Acting Director of National Intelligence Joseph Maguire has so far refused to share any details of the complaint with lawmakers, leading to an outcry among Democrats.
House Intelligence Chairman Adam Schiff, a Democratic California Congressman, praised the whistleblower for coming forward after a closed hearing with Mr Atkinson on Thursday.
He also accused the White House and Justice Department of intervening to block the complaint from being shared with Congress.
“I believe that there is an effort to prevent this information getting to Congress,” said Mr Schiff.
“And if the assertion is accurate… then at one level or another, it likely involves either the president or people around him.”