The confrontation occurred while Gonzales, now attorney general, was White House counsel and Ashcroft was U.S. attorney general. The Justice Department had rejected the controversial surveillance program and Gonzales allegedly went to Ashcroft to press the White House case.

Mueller, who had his own reservations about the warrantless domestic spying program, told the House Judiciary Committee Thursday he learned of the meeting shortly after Gonzales left Ashcroft's hospital room and was told the session dealt with the National Security Agency program, CNN reported.

Earlier this week, Gonzales told the Senate Judiciary Committee he hadn't discussed the program with Ashcroft.

Democrats are considering asking for a special counsel to investigate whether Gonzales perjured himself during his appearance.