President Trump's personal lawyer Rudy Giuliani has coffee with Ukrainian-American businessman Lev Parnas at the Trump International Hotel in Washington, September 20, 2019.

An attorney for Lev Parnas, an associate of President Donald Trump's personal lawyer, Rudy Giuliani, confirmed to NBC News Monday that his client would comply with requests for records and testimony from congressional impeachment investigators.

Parnas is believed to have played a key role as an intermediary in the alleged U.S. pressure campaign on the government of Ukraine to launch investigations that benefited Trump politically.

"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," said Parnas' attorney, Joseph Bondy, in a statement that was first reported Monday by Reuters.

Parnas is one of two Ukrainian Americans who helped Giuliani dig up dirt on Hunter Biden, the son of Trump's political rival, former Vice President Joe Biden. Hunter Biden once served on the board of a Ukrainian energy company.

Along with Igor Fruman, an associate, Parnas is also believed to have acted as a go-between for the Trump administration as it pursued a shadow foreign policy with Ukraine designed to aid in the president's reelection effort by tarnishing Biden and the Democratic party.

The agreement to comply with congressional requests represents an about-face for Parnas, whose previous lawyer, John Dowd, complained in October that the document and records requests his then-client had received were "overly broad."

It was unclear late Monday whether Fruman would also shift strategies and agree to cooperate with investigators. CNBC reached out to Fruman's lawyer, who did not immediately respond to questions about his client's intentions.

Parnas pleaded not guilty last month to campaign finance violations related to money he donated to a pro-Trump election committee, as well as money he helped raise to benefit a former Texas congressman.

The House investigation focuses on whether Trump abused the power of his office in his attempt to pressure Ukraine to investigate a political rival, and if so, whether those actions meet the standard for "high crimes and misdemeanors" deserving of impeachment and, potentially, removal from office.