WASHINGTON – The chairman of the Senate Judiciary Committee said yesterday that he has asked Attorney General Alberto Gonzales to testify during open hearings on the legality of the Bush administration’s domestic spying program.

A prominent conservative on the committee said he is troubled by the legal arguments the administration has presented for establishing the National Security Agency program.

President Bush has pointed to the congressional resolution that authorized him to use force against Iraq as allowing him to order spying within America without a warrant.

But Senator Brownback, a Republican of Kansas, said, “There was no discussion in anything that I was around that gave the president a broad surveillance authority with that resolution.”

The committee chairman, Senator Specter, a Republican of Pennsylvania, said senators will examine that issue and other legal questions in hearings scheduled for early February. Mr. Gonzales’s testimony is being sought because he is the principal spokesman for the administration’s position, Mr. Specter said.

The attorney general was White House counsel when Mr. Bush initiated the program, a role that could raise issues of attorney-client privilege in seeking his testimony. A message left with the Justice Department yesterday was not immediately returned.

Asked on CBS’s “Face the Nation” if Mr. Gonzales had agreed to appear, Mr. Specter said, “Well, I didn’t ask him if he had agreed. I told him we were holding the hearings and he didn’t object. I don’t think he has a whole lot of choice on testifying.”

Senator Schumer called for the former attorney general, John Ashcroft, and former deputy attorney general, Jim Comey, to testify at the hearings. “It would render these hearings useless and prevent the American people from getting to the bottom of this if the administration invoked executive privilege,” Mr. Schumer, a committee member, said in a statement.

Academics and others will be asked to appear, part of a list of witnesses “who think the president was right and people who think the president was wrong,” Mr. Specter said.

Slightly more than half of Americans, 56%, want the administration to obtain court approval before tapping into conversations inside America even if suspected terrorists are involved, according to an AP-Ipsos poll conducted last week. About four out of 10 agreed with the White House that court approval isn’t necessary.

Mr. Brownback, on ABC’s “This Week,” said the Senate Intelligence Committee also will hold hearings – closed to the public – on the NSA program.

“I think this is something that bears looking into and us to be able to establish a policy within constitutional frameworks of what a president can or cannot do,” said Mr. Brownback, considered a presidential hopeful for 2008.

He said he is “troubled by what the basis for the grounds that the administration says that they did these on, the legal basis, and I think we need to look at that far more broadly and understand it a great deal.”

The top Democrat on the Judiciary Committee said the hearings will provide the type of oversight that has been lacking.

“No matter who is in power, there should be real oversight,” Senator Leahy of Vermont said.

Mr. Leahy also dismissed Bush’s argument that the pre-war resolution allowed him to institute the secret program.

“We made it very clear what the president could do … also made it very clear what the president could not do. And he cannot do illegal spying on Americans,” Mr. Leahy said.

Senator Kennedy, a Democrat of Massachusetts, another Judiciary Committee member, said he agrees with those who believe wartime “is not a blank check to a president to override the rights and liberties that are in the Constitution of the United States.”

Mr. Kennedy added, “I don’t believe that this president understands that.”

After a story reporting the existence of the program appeared in the New York Times in December, Mr. Bush acknowledged that he had authorized the NSA to eavesdrop on conversations involving suspected terrorists in the months after the attacks of September 11, 2001. He contended that his constitutional powers and the pre-war resolution gave him that legal authority.

The NSA program bypassed the special court that Congress established in 1978 to approve or reject secret surveillance or searches of foreigners and American citizens suspected of terrorism or espionage.

The administration informed top members of Congress of the NSA program and, according to the president, administration officials regularly review its authorization.

Still, many members of Congress – Republicans as well as Democrats – have questioned whether the NSA program is outside the law.