Attorney General-nominee Michael Mukasey refused to say Thursday whether he considers waterboarding a form of torture, frustrating Democrats and potentially slowing his confirmation to head the Justice Department.

In an increasingly testy second day of hearings before the Senate Judiciary Committee, Mukasey also said he is reluctant to support legislation protecting reporters from being forced by courts to reveal their sources. The Democratic-led panel has approved those protections, which President Bush has threatened to veto.

Mukasey, a retired federal judge who ruled in some of the nation's highest-profile terror trials, repeatedly avoided discussing the legality of specific interrogation techniques — including forced nudity, mock executions and simulated drowning known as waterboarding.

To comment would be irresponsible "when there are people who are using coercive techniques and who are being authorized to use coercive techniques," Mukasey said.

"And for me to say something that is going to put their careers or freedom at risk simply because I want to be congenial — I don't think it would be responsible of me to do that," Mukasey said.

Instead, Mukasey stuck to his earlier definition of torture as illegal and unconstitutional — irritating Democrats who demanded a clearer answer.

"I'm hoping that you can at least look at this one technique and say that clearly constitutes torture, it should not be the policy of the United States to engage in waterboarding," said Sen. Dick Durbin, D-Ill.

"It is not constitutional for the United States to engage in torture in any form, be it waterboarding or anything else," Mukasey answered.

During terse questioning by Sen. Sheldon Whitehouse, D-R.I., Mukasey said he did not know if waterboarding is torture because he is not familiar with how it is done.

"If it's torture?" Whitehouse responded incredulously. "That's a massive hedge. I mean, it either is or it isn't."

"If it amounts to torture, it is not constitutional," Mukasey answered.

"I'm very disappointed in that answer," Whitehouse said. "I think it is purely semantic."

Mukasey looked down at his hands and took a deep breath.

Waterboarding has been banned by Congress, although the Bush administration has refused to say whether it is among the interrogation techniques prohibited in an executive order last summer.

Senate Judiciary Chairman Patrick Leahy, D-Vt., indicated he'll wait to get clearer answers from Mukasey before scheduling a committee vote to confirm him.

"I would think he would want to answer as quickly as he can," Leahy said.

Even so, Senate aides said they expect a vote on Mukasey by the end of the month at the latest.

White House spokesman Tony Fratto said Mukasey "is not in a position to discuss interrogation techniques" that are classified, such as waterboarding.

Mukasey "did not rule in or out any specific interrogation techniques," Fratto said.

Mukasey also irked senators who sought to pin him down on how much legal leeway he would give the president, as authorized in the Constitution, beyond laws that have been approved by Congress.

The struggle over the balance of power has been a hot topic during Mukasey's hearings, underscoring two issues confronting the Justice Department — the extent of presidential authority to eavesdrop on terror suspects, and congressional subpoenas to force administration aides to testify whether politics influenced the firings of nine U.S. attorneys last year.

Regarding the subpoenas, "we are at an impasse," said Sen. Arlen Specter of Pennsylvania, the panel's top Republican.

"We have tried to find a way of accommodating of what the president wants to do," Specter said. He asked Mukasey "to take a close look at it; see if you can help us resolve this impasse."

Specter also asked Mukasey to explain, in writing, specific objections to the proposed media shield law that protects reporters from revealing confidential sources. Mukasey told senators the law would hinder prosecutors and could protect bloggers who are also spies or terrorists.

"The system worked passably well up until now," Mukasey said.

Congress says a media shield is necessary to protect reporters and government whistleblowers who reveal improper or illegal official activity. Fifty news outlets, including The Associated Press, support the legislation.

Senators welcomed many of Mukasey's answers during three hours of testimony. He told Sen. Russ Feingold, D-Wis., that he would let posters be put up for events for gay and lesbian Justice Department employees. Posters have been banned in the past.

Mukasey also told Sen. Tom Coburn, R-Okla., that he would keep a sharp eye on the millions of dollars spent each year for employees to attend conferences.

The hearing, though testy at times, left little doubt that Mukasey would be easily confirmed.

"The real test is going to be what kind of attorney general you'll be," Leahy told Mukasey at the hearing's close.

Mukasey thanked senators for their support.

"The only thing I can tell you is if you ultimately do repose trust in me, I'm going to spend the next how many months it is trying to vindicate that trust," he said.