President Donald Trump's personal attorney has become a focus of the expanding congressional investigation into Russian meddling in the 2016 election.

Michael Cohen, one of Trump's longtime and closest confidants, told ABC News that both House and Senate investigators asked him "to provide information and testimony" about any contacts he had with people connected to the Russian government.

However, Cohen said he did not agree to their requests, according to ABC.

"I declined the invitation to participate, as the request was poorly phrased, overly broad, and not capable of being answered," he told ABC News in an email Tuesday. After Cohen rejected the congressional requests for cooperation, the Senate Select Intelligence Committee voted unanimously on Thursday to grant its chairman, Sen. Richard Burr of North Carolina, and ranking Democrat, Sen. Mark Warner of Virginia, blanket authority to issue subpoenas as they deem necessary. While much of the media focus in recent days has fallen on Russian contacts made by Trump's son-in-law, Jared Kushner, there are few people closer to the president than his longtime lawyer. Insiders consider Cohen to be Trump's pit bull or consigliere for his role in threatening legal action against Trump critics, gaining notoriety for threatening and browbeating reporters investigating Trump's background.

The attorney was one of Trump's most loyal flacks on the campaign trail, memorably clashing with CNN host Brianna Keilar last year about the validity of polls showing Hillary Clinton leading Trump.

Trump has derided the probe into Russian meddling and denied the allegations of his campaign colluding with the Russians.

Cohen's name joins a growing list of top members of Trump's orbit who are involved in the investigation, ABC reported.