Former White House national security adviser Michael Flynn declined on Monday to comply with a subpoena from the Senate Intelligence Committee as it investigates possible Russian interference in the 2016 U.S. election.
He invoked his Fifth Amendment protection against self-incrimination, as first reported by the Associated Press, citing sources close to Flynn, and confirmed by Senate aides.
The retired lieutenant general, a key witness in the Russia probe, sent a letter to the committee informing members of his decision.
Flynn's lawyer did not return requests for comment.
The Senate Intelligence Committee is conducting one of the main congressional probes into U.S. intelligence agency allegations of Russian meddling in the U.S. presidential election and whether there was any collusion between President Donald Trump’s campaign and Russia.
The committee first requested documents from Flynn in an April 28 letter, but he declined to cooperate with the request. Then it issued a subpoena.
It was not clear what the committee would do if Flynn decided not to comply.
Flynn was forced to resign as Trump's national security adviser in February, after less than a month on the job, for failing to disclose the content of his talks with Sergei Kislyak, Russia's ambassador to the United States, and then misleading Vice President Mike Pence about the conversations.
On Monday, Senator James Lankford, a Republican member of the intelligence panel, said on Twitter that Flynn was within his rights to invoke the Fifth Amendment of the U.S. Constitution.
“We will get to the truth one way or another,” Lankford said on Twitter. “We need facts, not speculation & anonymous sources.”
Congress has the constitutional authority to enforce a subpoena.
A Congressional Research Service report outlined three main options: seeking criminal prosecution through the executive branch, asking the courts for a civil judgment and using a dormant power of "inherent contempt" to detain and imprison an individual.
The latter option has not been used in 75 years, the report said, with Congress more often relying on the criminal contempt statute recently.
U.S. intelligence agencies concluded in January that Moscow tried to sway the November vote in Trump's favor. Russia has denied involvement, and Trump denies any collusion between his campaign and Russia.
Reuters reported on Thursday that Flynn and other advisers to Trump’s campaign were in contact with Russian officials and others with Kremlin ties in at least 18 calls and emails during the last seven months of the U.S. presidential race.
Two other former Trump associates - one-time campaign chairman Paul Manafort and Republican operative Roger Stone - have turned over documents the Senate panel had requested, while a third - campaign adviser Carter Page - had not yet complied, NBC News reported, citing a congressional source.
Flynn has acknowledged being a paid consultant to the Turkish government during the campaign.
(Reporting by Doina Chiacu, Patricia Zengerle, Tim Ahmann; Editing by Dan Grebler and Grant McCool)