House Oversight Committee Chairman Jason Chaffetz (R-Utah) indicated he's willing to issue a subpoena to obtain a memo authored by former FBI Director James Comey stating that President Trump asked Comey to stop the FBI's probe of former national security adviser Michael Flynn.

Chaffetz tweeted Tuesday night that his committee "is going to get the Comey memo, if it exists. I need to see it sooner rather than later. I have my subpoena pen ready."

Later Tuesday, Chaffetz sent a letter to acting FBI Director Andrew McCabe asking for all memos, summaries and recordings regarding Comey's communications with Trump.

Speaker Paul Ryan (R-Wis.), through a spokeswoman, expressed support for Chaffetz's move.

"We need to have all the facts, and it is appropriate for the House Oversight Committee to request this memo," Ryan press secretary AshLee Strong said.

The New York Times reported hours earlier that, according to a memo authored by Comey, Trump asked the FBI stop investigating Flynn over his ties to Russia.

"I hope you can let this go," Trump told Comey one day after Flynn resigned, according to the memo.

Comey's memo was part of an effort to create a paper trail documenting what he says was Trump improperly trying to influence the investigation. Trump fired Comey as FBI director a week ago.

The White House denied the contents of the memo and pointed to McCabe's testimony before the Senate Intelligence Committee last week, in which he said "there has been no effort to impede our investigation to date."

McCabe's statement was in response to a question from Sen. Marco Rubio (R-Fla.) about whether Comey's firing "in any way impeded, interrupted, stopped or negatively impacted" any FBI investigations.

Rep. Elijah Cummings (Md.), the top Democrat on the House Oversight Committee, called for Comey to testify in public.

"This is an explosive allegation, and it appears like a textbook case of criminal obstruction of justice," Cummings added.

He noted that Chaffetz had asked Comey to appear before the committee 48 hours after announcing last summer no charges would be brought against the-Democratic presidential nominee Hillary Clinton for her use of a private email server while secretary of State.

Cummings and Chaffetz asked the White House in March for documents regarding Flynn's payments from Russia for speaking engagements, but were denied. Cummings said Tuesday that the House Oversight Committee should issue a subpoena for those documents as well.

Flynn was ousted as Trump's national security adviser after it was revealed that he misled the senior White House officials about his contacts with the Russian ambassador during the transition about lifting sanctions.

The Obama administration had slapped new sanctions on Russia in December as retaliation for meddling in the U.S. presidential election last year.

Updated at 8:56 p.m.