WASHINGTON — President Trump’s nominee to lead the Justice Department’s criminal division, Brian A. Benczkowski, said on Tuesday that he helped Russia’s Alfa Bank investigate whether its computer servers contacted the Trump Organization.

Mr. Benczkowski had told the Senate Judiciary Committee last week that he represented Alfa Bank, which is one of Russia’s largest financial institutions and whose owners have ties to President Vladimir V. Putin.

On Tuesday, as Mr. Benczkowski came before the panel for his confirmation hearing, he acknowledged that his work for Alfa Bank directly touched on suspicions related to the bank in connection with the Trump-Russia affair.

Mr. Benczkowski said he had agreed to help his law firm, Kirkland & Ellis, represent Alfa Bank amid the intense scrutiny of the Trump-Russia investigation knowing that he might be nominated for a job in the Trump administration, a disclosure that prompted incredulity from several Democrats.