Washington (CNN) President Donald Trump's confidant Roger Stone is telling congressional committees that he would invoke his Fifth Amendment rights in order to not testify in response to requests for documents and testimony.

Stone's attorney Grant Smith rebuffed a request from the top Democrat on the Senate Judiciary Committee this week for documents and an interview connected to 2016 Russian election meddling. And Smith said he sent a similar letter to the Senate Intelligence Committee in September invoking the Fifth after the committee -- which is still conducting its investigation into Russian meddling -- requested documents and an interview.

Smith sent a letter to Sen. Dianne Feinstein of California stating that Stone was declining Feinstein's requests, which she released over Twitter on Tuesday.

"Mr. Stone's invocation of his Fifth Amendment privilege must be understood by all to be the assertion of a Constitutional right by an innocent citizen who denounces secrecy," the letter states.

Special counsel Robert Mueller is also investigating whether Stone was communicating with Julian Assange and WikiLeaks during the 2016 election either directly or through intermediaries. Mueller has spoken to a number of Stone's intermediaries, but he has still not reached out to Stone himself, Smith said.

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