Sampson said he resigned because he "let the attorney general and the department down" and "felt honor-bound to accept my share of the blame for this problem and to hold myself accountable."

His testimony does not specifically identify Gonzales as among top department officials aware of the plan. Gonzales has maintained he was not involved in the firings, although documents indicate he was briefed about it and now Democrats are calling for his resignation.

Sampson's testimony also addresses the issue of whether the firings were politically motivated beyond the usual process of replacing U.S. attorneys who were appointed under a previous administration.

Sampson said the distinction "between 'political' and 'performance-related' reasons for removing a United States Attorney is, in my view, largely artificial," emphasizing that there is a difference why political appointees can be asked to resign versus a "civil servant or private sector" employee.

"Presidential appointees are judged not only on their professional skills but also their management abilities, their relationships with law enforcement and other governmental leaders, and their support for the priorities of the president and the attorney general," according to his testimony.

Sampson created a list of attorneys that might be replaced based on that definition and sought advice from fellow Justice Department employees and "provided that information to the White House when requested."

"Based on everything I have seen and heard, I believe that each replaced U.S. Attorney was selected for legitimate reasons falling well within the President's broad discretion," according to his testimony.

The Justice Department on Wednesday released more documents that lay the blame for the debacle at Sampson's feet.

Sampson wrote a Feb. 23 letter, signed by Assistant Attorney General Richard Hertling and sent to four Senate Democrats, that may have had "inaccurate or incomplete information" similar to that found in the congressional testimony, according to the documents.

Among the additional 202 e-mails submitted to the House and Senate judiciary committees on Wednesday is a cover letter by Hertling that says a review found that "certain statements in the February 23 letter are contradicted by Department documents included in our production in connection with the Committees' review of the resignations of U.S. Attorneys."

"We sincerely regret any inaccuracy," Hertling said.

The latest document pile mainly includes e-mails from Sampson organizing Hertling's response, including sending it to the White House for approval because it "mentions Rove and alludes to Harriet (Miers)," according to a Feb. 22 e-mail.