WASHINGTON (CNN) -- Arkansas Democratic Sen. Mark Pryor bluntly accused Attorney General Alberto Gonzales of lying to the Senate about replacing federal prosecutors with interim appointees and joined calls for Gonzales' resignation Thursday.

"When an attorney general lies to a United States senator, I think it is time for that attorney general to go," Pryor said on the Senate floor.

"He did not only lie to me as a person, but when he lied to me, he lied to the Senate and to the people I represent."

Under a provision of the antiterrorist USA Patriot Act, interim appointees can serve indefinitely without facing Senate confirmation.

Justice Department officials initially told Congress the removals of eight attorneys were performance-related, which prompted an outcry from the fired lawyers. U.S. attorneys are routinely replaced when a new president takes office, but their removal in the middle of a presidential administration is rare -- and some say unprecedented.

Most of the federal prosecutors claim they were the political casualties of rankling the White House, and some say they were pressured by members of Congress to expedite politically charged cases.

The administration later admitted one of the fired prosecutors, U.S. attorney H.E. "Bud" Cummins in Little Rock, Arkansas, had been removed to make way for a Timothy Griffin, a former aide to White House political adviser Karl Rove.

The administration said the remainder were fired over management concerns and policy disagreements.

When asked about the matter in January, Gonzales told the Senate Judiciary Committee the Bush administration planned to replace the interim appointees with nominees who would be confirmed by the Senate.

But documents released after Monday's resignation of Gonzales' chief of staff, Kyle Sampson, showed Sampson hoped to "run out the clock" and keep Griffin, a former aide Rove, in place over the objections of Pryor and his Arkansas colleague, Blanche Lincoln.

The Justice Department did not respond to Pryor's accusations, but White House spokesman Tony Snow said Gonzales continues to enjoy President Bush's confidence.

Bush said Wednesday he is "not happy" about mistakes surrounding the decision to fire the eight attorneys, but his faith in his attorney general is unwavering. (Watch Bush defend Gonzales but express displeasure Video)

Gonzales said Tuesday that Sampson was in charge of the shakeup and was asked to resign for failing to share information with other Justice Department officials. That failure led to Justice Department officials giving "incomplete" explanations for the shakeup to Congress, the attorney general said.

A lawyer for Sampson declined comment when contacted by CNN.

Tuesday's disclosures have led to calls for Gonzales' head from several Democratic senators and one Republican, New Hampshire's John Sununu.

In a voice vote earlier Thursday, the Senate Judiciary Committee authorized the use of subpoenas to elicit testimony from five current and former Justice Department officials in the probe into the dismissals of the eight attorneys. Subpoenas were authorized for six of the attorneys as well.

"If I do not get the cooperation, I will subpoena," said Sen. Patrick Leahy, the panel's chairman, during the hearing. "We will have testimony under oath before this committee. We'll have the chance for both Republicans and Democrats to ask questions, and we'll find out what happened."

But the committee's ranking Republican warned against moving too hastily.

"I think the subpoena issue has to be handled with great delicacy because when a subpoena is issued there is a suggestion that the person will not come in voluntarily," said Sen. Arlen Specter of Pennsylvania. "When the person will not come in voluntarily, there is a suggestion that the person has something to hide."

The committee postponed a vote on the authorization to use subpoenas to compel White House officials to testify, including Rove and former White House counsel Harriet Miers.

Chairman: Committee 'misled'

Leahy, a Democrat from Vermont, said Wednesday he told Gonzales that he was "furious" with how his department handled the dismissals. (Watch Leahy insist on testimony under oath Video)

The senator went on to say he felt Gonzales and Deputy Attorney General Paul McNulty were less than forthcoming when they attended earlier hearings on the matter.

"I believe that they misled my committee. Whether it was deliberate or not is what we're going to have to find out," Leahy said.

Leahy delivered his remarks -- and his threat to subpoena members of the Bush administration, including Rove -- as Sununu became the first Republican senator to call for Gonzales' head.

Leahy bristled at the idea that Gonzales and White House counsel Fred Fielding would decide whether to "allow" members of the administration to testify.

In remarks directed toward Fielding, Leahy said, "Frankly, I don't care whether he says he's going to allow people or not. We'll subpoena the people we want. If they want to defy the subpoena, then you get into a stonewall situation I suspect they don't want to have."

The senator recalled a conversation he had with Gonzales in which the attorney general said there were low-level Justice Department staffers he didn't want to testify.

"I said, frankly, Mr. Attorney General, it's not your decision. It's mine and the committee's. We will have subpoenas. I would hope that they will not try to stonewall subpoenas," Leahy said.

Gonzales acknowledges mistakes

Gonzales conceded Wednesday he "absolutely" should have been more involved in the decision to fire the eight prosecutors.

The attorney general said he charged Sampson with determining "where we could do better" after Miers, then-White House counsel, suggested firing all 93 U.S. attorneys, an idea Gonzales says he opposed.

Sampson came back with the list of names of eight U.S. attorneys whose dismissals have sparked the political furor.

Sununu said Wednesday that Gonzales should follow suit or be replaced.

"The president should fire the attorney general and replace him as soon as possible with someone who can provide strong, aggressive leadership," Sununu said in a statement. (Watch Gonzales navigate a minefield of questions Video)

Sununu said Gonzales had lost all credibility because of the firings, controversy over renewal of the USA Patriot Act and a report last week that the FBI had underreported its use of national security letters to snoop on Americans. "These failures have created a deep, widespread lack of confidence," Sununu said.

Snow said Bush was disappointed with Sununu's stance.

CNN's Dana Bash, Ed Henry, Terry Frieden and Suzanne Malveaux contributed to this report.

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