U.S. Treasury Secretary Steven Mnuchin declined to tell lawmakers who purchased his entertainment company, but promised it wasn't a Russian.

"I can assure you that it's not a Russian oligarch or any Russian," Mnuchin said Tuesday in testimony before the House Financial Services Committee. "I don't believe I've ever met a Russian oligarch."

Mnuchin has faced questions over reports that a company linked to Ukrainian-born billionaire Len Blavatnik purchased a stake in Mnuchin's company RatPac-Dune Entertainment in 2017, after he became Treasury chief. Democratic lawmakers have said such a transaction would create a conflict of interest for Mnuchin, because Blavatnik is a business associate of Russian billionaire Oleg Deripaska, the target of U.S. sanctions aimed at President Vladimir Putin's inner circle.

The Treasury Department said in a January letter that Mnuchin didn't sell his stake in RatPac-Dune to Blavatnik or any of his firms, but didn't identify the buyer. Mnuchin's stake, which he was required to sell under an agreement with the Office of Government Ethics before he was confirmed as Treasury secretary, was sold to "a third party unconnected to Blavatnik," Treasury said.

Speaking Tuesday, Mnuchin reiterated that statement and said the transaction was "confidential."