WASHINGTON (AP) — Federal prosecutors are planning to interview an executive with Ukraine's state-owned gas company as part of an ongoing probe into the business dealings of Rudy Giuliani and two of his Soviet-born business associates.

A lawyer for Andrew Favorov confirmed Tuesday that he is scheduled to meet voluntarily with the U.S. Justice Department. Favorov is a director at Naftogaz, the state-owned gas provider in Ukraine.

Prosecutors are investigating the business dealings of Giuliani, President Donald Trump's personal lawyer, including whether he failed to register as a foreign agent.

The Associated Press reported in October that Giuliani associates Lev Parnas and Igor Fruman approached Favorov at a March energy conference in Houston with a proposed deal to export U.S. gas to Ukraine. Parnas and Fruman were arrested on numerous charges last month.