Lev Parnas had initially refused to comply with the request for documents from House impeachment investigators.
A Rudy Giuliani associate who was indicted last month for making illegal campaign contributions is willing to provide documents and testimony to House impeachment investigators, his lawyer confirmed to NBC News.
Lev Parnas' lawyer Joseph A. Bondy said, "We will honor and not avoid the committee's requests to the extent they are legally proper, while scrupulously protecting Mr. Parnas' privileges including that of the Fifth Amendment."
His change of heart was first reported by Reuters on Monday.
The Florida businessman is a key figure in the Trump administration's dealings with the Ukrainian government.
He and Igor Fruman, another Florida businessman with ties to Ukraine, helped President Donald Trump's personal lawyer Rudy Giuliani hunt for dirt there on former Vice President Joe Biden and his son.
They also were also involved in the effort to oust U.S. ambassador to Ukraine Marie Yovanovitch, whose testimony before the House committee was released Monday.
Parnas and Furman's former lawyer, John Dowd, had told Congress in a letter last month that the pair might not be able to give Congress all the documents they had requested in part because they "assisted Mr. Giuliani in connection with his representation of President Trump. Mr. Parnas and Mr. Furman have also been represented by Mr. Giuliani in connection with their personal and business affairs."
"Thus," the letter said, "certain information you seek" is "protected by the attorney-client, attorney work product and other privileges."
Parnas has pleaded not guilty to the charges against him and is currently free on $1 million bond.
The House Intelligence Committee subpoenaed Parnas after his arrest.