WASHINGTON (AP) – The top aide to Attorney General Alberto Gonzales abruptly quit on Friday, almost two weeks after telling Congress she would not testify about her role in the firings of federal prosecutors.

“I am hereby submitting my resignation to the office of attorney general,” Monica M. Goodling said in a three-sentence letter. There was no immediate reason given, but her refusal to face Congress had intensified a controversy that threatens Mr. Gonzales’ job.

Asserting her Fifth Amendment right against self-incrimination, Ms. Goodling had rejected demands for a private interview with a House committee investigating the firings.

Ms. Goodling was senior counsel to Mr. Gonzales and was the department’s White House liaison before she took a leave amid the uproar over the prosecutors’ ousters.

Calling her five-year stint at Justice an honor, Ms. Goodling told Mr. Gonzales in her letter, “May God bless your richly as you continue your service to America.”

Ms. Goodling is at the center of the controversy because, as the bridge between the Justice Department and the White House, she may be best suited to explain how deeply Karl Rove and other members of President Bush’s political team might have been involved in the firings. Congress also wants her to testify on Mr. Gonzales’ role in light of his shifting explanations.

Her resignation comes less than two weeks before Gonzales’ own planned testimony to Congress, which may determine his fate as attorney general. Several Republican lawmakers have joined Democrats in expressing deep dissatisfaction with him over the firings and other matters at Justice.