Dan Coats, the nation's top intelligence official, is testifying before Congress after reports that President Donald Trump may have personally asked him to try to quash the FBI's investigation of former National Security Adviser Michael Flynn.

The Washington Post reported Tuesday that Coats, Trump's director of national intelligence, told associates in March that the president asked him to intervene with FBI Director James Comey to get the FBI to cool its investigation of Flynn's alleged ties to Russia.

Coats' spokesman, however, on Tuesday night told NBC News that Coats "has never felt pressured by the president or anyone else in the administration to influence any intelligence matters or ongoing investigations."

The spokesman, Brian Hale, gave no further details, saying, "Director Coats does not discuss his private conversations with the president."

Coats is likely to be questioned extensively about the report as he testifies before the Senate Intelligence Committee. Acting FBI Director Andrew McCabe, National Security Agency Director Michael Rogers and Deputy Attorney General Rod Rosenstein will also be appearing before the committee.

National Intelligence Director Dan Coats testifies before the Senate Armed Services Committee on May 23. Mark Wilson / Getty Images

It's not clear how much of Coats' take on the report will become public, however. The first part of the hearing — which was called to review the Foreign Intelligence Surveillance Act, the law used to authorize surveillance of Americans — will be open, but the hearing is scheduled to move into a closed session afterward.

Flynn resigned Feb. 13, following reports that he misled Vice President Mike Pence about his conversations with Russia's ambassador to the United States.

The Washington Post reported that on March 22 Coats was among several other officials at a briefing for Trump at the White House. As the briefing ended, the president asked everyone to leave except for Coats and CIA Director Mike Pompeo.

It was then that Trump started complaining about the Flynn investigation, The Post reported, citing officials familiar with the account that Coats gave to his associates.

NBC News reported last month that Comey wrote internal memos expressly saying Trump had tried to intervene directly with him, as well, to stall the investigation.

If the new report is true, "this is obstruction of justice," said Rep. Ted Lieu, D-California, a member of the Foreign Relations Committee and a former Air Force prosecutor.

Trump appears to have been "endeavoring to influence an investigation," Lieu said in an interview Tuesday night on MSNBC's "All In With Chris Hayes." "We've seen so much evidence of this.

"I don't know why people tiptoe around this, say it looks like it or could be," Lieu added. "It is obstruction of justice."