WASHINGTON (AP) — Attorney General Eric Holder on Tuesday fended off Republican demands that he appoint a special counsel outside of the Justice Department to look into national security leaks.

Holder said both he and FBI Director Robert Mueller have already been interviewed by the FBI as part of a fast-moving Justice Department leak investigation.

At a Senate Judiciary Committee hearing, Sens. Lindsey Graham, R-S.C., and Chuck Grassley, R-Iowa, said they want the attorney general to appoint a special counsel to look into the leaks, rather than Holder’s choices, U.S. Attorneys Ron Machen and Rod Rosenstein, who hold politicalappointments.

Graham and Grassley were referring to a procedure by which a special counsel appointed from outside the Justice Department conducts the leak investigations.

Holder praised the two U.S. attorneys as experienced and highly respected.

“We have people who have shown independence, an ability to be thorough and who have the guts to ask tough questions,” Holder told the committee. “And the charge that I’ve given them is to follow the leads wherever they are, whether it is — wherever it is in the executive branch or some other component of government. I have great faith in their abilities.”

Machen and Rosenstein were appointed to oversee investigations into who leaked information about U.S. involvement in cyberattacks on Iran and an al-Qaida plot to place an explosive device aboard a U.S.-bound flight.

Not far from where Holder was testifying, Sen. John McCain, President Barack Obama’s 2008 rival and the harshest critic of the White House over the leaks, introduced a non-binding resolution calling for a special counsel. He was joined by more than a dozen GOP senators in pressing for the measure.

McCain called it the “almost unprecedented release of information which directly affects our national security. I can’t think of any time that I have seen such breaches of ongoing national security programs as has been the case here.”

At the Senate committee hearing, Holder pointed out that the Obama administration has brought more leak prosecutions than any other administration. The Obama administration has charged six people under the Espionage Act for the alleged mishandling of classified information.

Holder told the committee that speed in carrying out the leak probes was an important factor in appointing the two prosecutors.

Holder cited the quick interviews of him and Mueller as one illustration of that speed.

“That interview was not some kind of pro forma take it easy interview. I mean, these were serious — a serious interview that was done by some serious FBI agents,” said Holder. “The same thing happened to the director of the FBI as well because we were people who had knowledge of these matters,” that were the subjects of the leaks.

Holder estimated that about 100 interviews have already been completed.

Finding a special counsel would take time, he said, and it would take more time to get an outside appointee up to speed on the details of the ongoing probe.

“There are clearly people around the president leaking stories that involve highly classified information” favorable to the Obama administration, Graham told Holder. If there is “ever a need” for an outside special counsel, it is now.

Graham said it was correct for the administration of former President George W. Bush to appoint a special counsel to investigate officials for leaking the identity of CIA employee Valerie Plame.

The Plame leak was investigated by a U.S. attorney, “the same thing I have done here,” Holderreplied. The attorney general was referring to the U.S. Attorney in Chicago, Patrick Fitzgerald, who led the investigation and prosecuted Bush White House aide “Scooter” Libby.

Sen. John Cornyn said Machen, a contributor to Barack Obama’s presidential campaign, was toopolitically partisan to handle the leak probes.

Republicans interspersed their criticism of Holder about the leak probes with criticism of his failure to turn over more documents to a House committee investigating a flawed gun-smuggling probe in Arizona, Operation Fast and Furious.

Regarding Fast and Furious, Cornyn called on Holder to resign. He said the attorney general had misled Congress in February by embracing a letter to Congress denying there were problems. Hundreds of illicitly purchased weapons wound up south of the border, many of them at crime scenes.

Holder offered to sit down with Republicans and reach an accommodation to avoid what the attorney general characterized as an impending constitutional crisis over Justice Department documents the attorney general says involve highly sensitive law enforcement investigations and prosecutions.

Republicans on the House Oversight and Government Reform Committee have scheduled a June 20 vote on a proposed contempt of Congress citation directed at Holder for not turning over the material.

On the Senate floor, Graham, R-S.C., said that not appointing a special counsel would set a “precedent that will haunt the country and this body and future White Houses in a way that I think is very disturbing.”

Both Republicans quoted Democratic demands during George W. Bush administration for a special counsel in the disclosure of Plame’s identity.

McCain’s move to get swift Senate passage of his resolution was blocked by Democratic Sen. Ron Wyden of Oregon, who said the effort was premature.