Former US national security adviser Michael Flynn will invoke his 5th Amendment protection against self-incrimination and will not hand over documents to the probe into Russian interference in the 2016 election, sources said.
Mr Flynn's decision comes less than two weeks after the US Senate Intelligence committee issued a subpoena for his personal documents.
Legal experts have said Mr Flynn is unlikely to turn over the documents without immunity because he would be waiving some of his constitutional protections by doing so.
Mr Flynn has previously sought immunity from "unfair prosecution" to cooperate with the committee.
The Senate committee is one of several congressional inquiries investigating possible collusion between Russia and US president Donald Trump's 2016 campaign.
Mr Flynn is also the target of other congressional investigations as well as an ongoing FBI counter-intelligence probe and a separate federal investigation in Virginia.
Mr Flynn, a retired US army lieutenant general, was sacked from his position as Mr Trump's national security adviser in February.
At the time, Mr Trump said he sacked Mr Flynn because he misled senior administration officials, including vice-president Mike Pence, about his contacts with Russian officials.
Members of key congressional committees are pledging a full public airing as to why former FBI director James Comey was ousted amid an intensifying investigation into Russia's interference with the US election.
Both Republican and Democratic politicians said they will press Mr Comey in hearings as to whether he ever felt that Mr Trump tried to interfere with his FBI work.
Others are insisting on seeing any White House or FBI documents that detail conversations between the two, following a spate of news reports that Mr Comey had kept careful records.
Mr Comey was sacked by the US president earlier this month.
The former FBI director has agreed to testify before the Senate intelligence committee.
