WASHINGTON, March 29 — The former chief of staff to Alberto R. Gonzales testified on Thursday that he had consulted regularly with the attorney general about dismissing United States attorneys, disputing Mr. Gonzales’s public account of his role as very limited.

The former aide, D. Kyle Sampson, who resigned two weeks ago, told the Senate Judiciary Committee that Mr. Gonzales’s statements about the prosecutors’ dismissals were inaccurate and that the attorney general had been repeatedly advised of the planning for them.

The two men talked about the dismissal plans over a two-year period, Mr. Sampson said, beginning in early 2005 when Mr. Gonzales was still the White House counsel. Mr. Sampson said he had briefed his boss at least five times before December 2006, when seven of the eight prosecutors were ousted.

Asked by Senator Arlen Specter, Republican of Pennsylvania, about Mr. Gonzales’s statements at a March 13 news conference that he had not participated in any discussions about the dismissals, Mr. Sampson replied, “I don’t think the attorney general’s statement that he was not involved in any discussions about U.S. attorney removals is accurate.”

Mr. Sampson’s testimony was the latest blow to Mr. Gonzales, who is struggling to keep his job as lawmakers from both parties have called for his resignation and prosecutors in his agency have criticized him privately. The attorney general has promised to remain in his post, and President Bush has backed him publicly.

The White House repeated that support on Thursday, while acknowledging disappointment with Mr. Gonzales’s handling of the dismissals.

“The attorney general has some work to do up on Capitol Hill,” said Dana Perino, a White House spokeswoman, adding that President Bush “wasn’t satisfied with incomplete or inconsistent information being provided to Capitol Hill.”

Brian Roehrkasse, a Justice Department spokesman, said the attorney general had already begun to set the record straight in a television interview on Monday by saying that Mr. Sampson had occasionally updated him on the planned dismissals.

In his daylong appearance on Thursday, Mr. Sampson shed no new light on why Harriet E. Miers, the former White House counsel, first proposed the dismissals after the 2004 election. And he offered little information clarifying whether Karl Rove, the senior White House adviser, played a central role.

While denying that the Bush administration had replacement candidates in mind when the prosecutors were ousted, Mr. Sampson acknowledged that complaints from Republican lawmakers were a factor in the dismissals of two prosecutors.

Mr. Sampson also acknowledged publicly for the first time that he proposed replacing Patrick J. Fitzgerald, the United States attorney in Chicago, at a White House meeting in 2006. Mr. Fitzgerald was then prosecuting the case involving the leak of the identity of Valerie Wilson, the C.I.A. officer. That led to the conviction this month of I. Lewis Libby, Vice President Dick Cheney’s former chief of staff, on perjury charges.

“I said Patrick Fitzgerald could be added to this list,” Mr. Sampson said, recalling a conversation with Ms. Miers and an aide. The suggestion, which he said he regretted, was immediately dropped. “They looked at me like I had said something totally inappropriate, and I had,” Mr. Sampson said.

Asked whether Mr. Rove, who testified several times before Mr. Fitzgerald’s grand jury, had ever expressed an opinion about removing Mr. Fitzgerald, Mr. Sampson said: “To the best of my recollection, no. I don’t remember that.”

As he answered sometimes skeptical questions from senators of both parties, Mr. Sampson, who sat alone at the witness table in a packed Senate hearing room, offered an apologetic and deferential account of his actions. At times, he put his hand on his chest or heart, or tapped the table before him, to emphasize his points. But he grew testy at times and more defensive as the morning hearing wore into the afternoon.

Mr. Sampson, who testified voluntarily, seemed eager to explain his own actions, admit his mistakes and rebut speculation that the dismissals were intended to block or accelerate corruption inquiries.

“Looking back on all of this, I wish that we could do it over again,” Mr. Sampson said, in the closing minutes of the hearing. “In hindsight, I wish the department had not gone down this road at all.”

Mr. Sampson said he regretted his role in what he said had become “an ugly undignified spectacle.” He added, “This episode has been personally devastating to me and my family.”

Much of the hearing focused on why prosecutors’ names were added to or dropped off the list. At regular White House meetings that included Ms. Miers and her deputy, William Kelley, progress on preparing the list was discussed, Mr. Sampson said.

He repeatedly rebuffed questions suggesting that any of the dismissals occurred for inappropriate political reasons. But he conceded that complaints by Republican political figures most likely played a role in ousting David C. Iglesias in New Mexico and Carol C. Lam in San Diego.

Mr. Sampson acknowledged that as recently as 2005, he had considered Mr. Iglesias an “up and comer” who could be a candidate for promotion to Justice Department headquarters.

But Mr. Sampson said that shortly before the November 2006 election, Mr. Rove complained to Mr. Gonzales about Mr. Iglesias and two other prosecutors — Mr. Sampson did not identify them — considered to be insufficiently aggressive in pursuing voter fraud cases. Mr. Rove was forwarding objections raised by prominent Republicans, including Senator Pete V. Domenici of New Mexico.

Mr. Domenici’s criticism played a role in adding Mr. Iglesias’s name to the ouster list, or at least keeping it there, Mr. Sampson said. “Senator Domenici won’t mind if he stays on the list,” Mr. Sampson said, recalling a comment by Deputy Attorney General Paul J. McNulty.

Mr. Sampson disputed suggestions that Ms. Lam was removed because of her office’s corruption investigation of former Representative Randy Cunningham, a Republican, who was convicted in 2005.

“The real problem at that time was her office’s prosecution of immigration cases,” Mr. Sampson said. But he said he did not think she was told of concerns that her office was failing to prosecute enough border smugglers before she was ousted.

None of the dismissals were intended to interfere with political corruption investigations, he said. “During this process, I never associated asking the U.S. attorneys to resign with any investigation,” Mr. Sampson said.

Instead, he said, he drew up the dismissal list, adding and subtracting names, based on a “not scientific” accumulation of opinions and other information from Justice Department officials.

Mr. Sampson said respect for priorities set by the administration, like prosecuting large numbers of gun crimes or border smuggling cases, was a justifiable reason for including prosecutors on the ouster list.

“Let me just say that in my e-mails, by referring to ‘loyal Bushies’ or ‘loyalty to the president and the attorney general,’ what I meant was loyalty to their policies and to the priorities that they had laid out for U.S. attorneys,” Mr. Sampson said.

The problem, he agreed, was the way the process was handled; to outside observers, he acknowledged, it may have incorrectly appeared as if prosecutors were being replaced because of their role in pursuing politically sensitive corruption cases.

“I personally did not take adequate account of the perception problem that would result,” he said.

Several senators questioned how he could have drafted a letter sent to the Senate in February claiming that Mr. Rove had played no role in the appointment of J. Timothy Griffin, the interim United States attorney in Arkansas and a former Rove aide. Mr. Sampson had written an e-mail message to his colleagues acknowledging that Mr. Rove wanted Mr. Griffin to get the job.

He tried to explain the contradiction by suggesting that what he knew for sure was that Mr. Rove’s staff wanted Mr. Griffin to get the job, a response that seemed to satisfy few members of the committee.

Mr. Specter also pressed Mr. Sampson to explain who else in the Bush administration considered using a provision included in the 2006 reauthorization of the USA Patriot Act to name United States attorneys permanently without Senate confirmation. Mr. Sampson finally acknowledged that others in the administration whom he did not name favored using that power to keep Mr. Griffin in the Arkansas post.

“In hindsight, I believe that it would be an abuse of the attorney general’s appointment authority,” to have used the Patriot Act provision, Mr. Sampson said, even though he conceded that he had strongly advocated that the attorney general do just that.

Many of the Republicans on the Judiciary Committee, including Senators Jon Kyl of Arizona, Jeff Sessions of Alabama and Charles E. Grassley of Iowa, made it clear that like the Democrats they remained extremely disappointed with the way the dismissals had been handled and explained.

“The bottom line is we shouldn’t have conflicting statements coming from somebody who is the top law enforcement officer of the United States, or his staff,” Mr. Grassley said. “We expect them to be prepared to answer questions. Congress and the American people ought to get a consistent story, and we ought to be able to expect the truth.”