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WASHINGTON (Reuters) - Michael Cohen, one of President Donald Trump’s closest business advisers, said on Sunday he would testify on Tuesday to the U.S. Senate Intelligence Committee, as the panel investigates alleged Russian interference in the 2016 U.S. election.

The timing of Cohen’s testimony was first reported by NBC. Cohen confirmed that he would testify to the committee on Tuesday and said he did not know whether it would be in a closed session or public.

Aides to the committee’s leaders did not immediately respond to requests for comment.

Cohen said previously he had received a subpoena from at least one of the congressional committees investigating what U.S. intelligence has determined were Russia’s efforts to influence the election on Trump’s behalf, and whether Trump associates colluded with Russia.

Russia denies such activity. The White House denies any collusion, but concerns about the issue and Trump’s ties to Russia have shadowed the first months of the Republican’s presidency.

Cohen, a personal attorney to Trump, would be one of a series of close associates of the president to testify in Congress. Members of both the Senate and House of Representatives committees conducting investigations have said they expect to call more.

Trump’s oldest son, Donald Trump Jr., testified to the Senate Judiciary Committee earlier this month.