"I have decided to follow my lawyer's advice and respectfully invoke my constitutional right," Monica Goodling, Gonzales' counsel and White House liaison, said in a statement to the Senate Judiciary Committee.

The revelation complicated the outlook for Gonzales, who is traveling out of town this week even as he fights to keep his job and his agency's investigatory power.

In an interview with NBC News, Gonzales said Monday he was "really pained" by Republicans and Democrats alike who widely say the attorney general has lost his credibility.

Asked why he would want to remain as attorney general amid so many calls for his ouster, Gonzales said he's been asking himself lately whether it's appropriate for him to stay in his job.