Former US national security adviser Michael Flynn will refuse to hand over files to the Senate panel probing alleged contact Russian political meddling, US media reports.
Michael Flynn resigned just weeks after being appointed national security adviser. Photo: AFP
Mr Flynn plans to invoke his Fifth Amendment right against self-incrimination, the reports say.
The Senate Intelligence Committee is investigating possible links between Donald Trump's presidential campaign and the Kremlin.
Mr Flynn left the national security adviser role in February, after it emerged he lied about the nature of his contacts with the Russian ambassador.
The committee issued a subpoena two weeks ago to obtain the documents.
The FBI and two congressional committees are investigating claims that Russian hackers tried to help Mr Trump win last November's presidential election, and that members of his election campaign colluded with the alleged Kremlin conspiracy.
My Flynn's lawyer has previously demanded immunity from "unfair prosecution" in order to co-operate with the committee.
The Fifth Amendment to the US constitution protects Americans from being legally compelled to testify against themselves in a criminal case.
Last week the committee's chairman Senator Richard Burr told reporters that Mr Flynn was "not cooperating" with the investigation, adding that they had not received "a definitive answer" on whether he would testify.
Mr Flynn is also being investigated by the Department of Defense, after it was revealed that he received payments from Russia and Turkey shortly after leaving the Pentagon.
Former acting Attorney General Sally Yates testified to senators this month that she had warned the White House 18 days before Mr Flynn was fired that he was vulnerable to Russian blackmail.
The Russians had "leverage" over the ex-national security adviser, Mrs Yates testified, adding that her concerns were of a legal nature, and were not simply a "trust issue" between the president and his staff.
Mr Flynn has been accused of discussing lifting US sanctions on Russia during his conversation with Moscow's envoy Sergei Kislyak before Mr Trump took office.
If Mr Flynn continues to refuse to comply with Senate investigators, it is thought they could vote to hold him in contempt of Congress, or even refer his case for possible criminal charges.
Mr Flynn is also at the centre of an FBI investigation into possible collusion between the Trump presidential campaign and Russia.
Former FBI director Robert Mueller was appointed last week to lead the FBI investigation following Mr Trump's firing of the law enforcement agency's director, James Comey.
Attorney General Jeff Sessions has been forced to recuse himself from that investigation after he neglected to tell senators about his meeting with Mr Kislyak during his confirmation hearings.
- BBC