CIA director nominee Michael Hayden acknowledged concerns about civil liberties even as he vigorously defended the Bush administration's warrantless eavesdropping program as a legal spy tool needed to ensnare terrorists.

CIA nominee Air Force Gen. Michael Hayden testifies on Capitol Hill, Thursday, May 18, 2006 at his confirmation hearing before the Senate Intelligence Committee. [AP]

Peppered with tough questions at a daylong confirmation hearing Thursday, the four-star Air Force general portrayed himself as an independent thinker, capable of taking over the CIA as it struggles with issues ranging from nuclear threats to its place among 15 other spy agencies.

Hayden spoke of his own concerns about the no-warrant surveillance program and other eavesdropping operations he oversaw as National Security Agency chief from 1999 until last year.

"Clearly, the privacy of American citizens is a concern constantly," he told the Senate Intelligence Committee. "And it's a concern in this program. It's a concern in everything we've done."

Hayden said he decided to go ahead with the terrorist surveillance program in October 2001 after internal discussions about what more the NSA could do to detect potential attacks. He believed the work to be legal and necessary, an assertion Democrats and civil liberties groups have aggressively questioned.

"The math was pretty straightforward," Hayden said. "I could not not do this."

Bush selected Hayden to be the nation's 20th CIA director earlier this month, knowing his choice would inflame the debate about the NSA program to monitor domestic calls and e-mails when one person is overseas and terrorism is suspected. Breaking new ground, the work was done without court approval.

A USA Today report last week about NSA efforts to analyze the call records of millions of Americans added new grist to the discussion and prompted the administration to reverse course after five months and tell the intelligence committees on Wednesday more about the terror-monitoring work.

Hayden declined to openly discuss the reports, saying he would talk only about the part of the program the president had confirmed.

"Is that the whole program?" asked Sen. Carl Levin (news, bio, voting record), D-Mich.

"I'm not at liberty to talk about that in open session," replied Hayden, currently the nation's No. 2 intelligence official. A closed-door session was held in the evening.

Even as Republicans praised Hayden, senators of both parties said they should have been briefed on the work five years ago. More than one Democrat said he felt deceived.

Sen. Russ Feingold (news, bio, voting record), D-Wis., said he was convinced the program was illegal and questioned whether the phone calls of Americans not linked to al-Qaida were ever captured. Hayden didn't answer directly.

"If you're using a 'probable cause' standard as opposed to absolute certitude," he said, "sometimes you may not be right."

If confirmed, Hayden would take over a struggling CIA, groping to define its role after the 2004 overhaul of the spy community in response to the mistakes on Sept. 11, 2001, and the prewar Iraq intelligence. Hayden, who frequently uses sports metaphors, said he believes U.S. spy agencies have become "the football in American political discourse."

"I also believe it's time to move past what seems to me to be an endless picking apart of the archaeology of every past intelligence success or failure," he said.

Hayden pledged to reform the agency by focusing on traditional spycraft and the quality of intelligence analysis. He also said he'd give policy-makers the unvarnished truth, a reference to criticisms of the spy agencies in the run-up to Iraq.

"When it comes to speaking truth to power, I will lead CIA analysts by example," he said. "I will, as I expect every analyst will always give our nation's leaders the best analytic judgment."

Some lawmakers questioned whether Bush should choose a military officer to run the civilian spies at the CIA, in an era when the Defense Department is increasingly involved in intelligence.

Hayden, a 37-year Air Force officer, tried to show he could disagree with Defense Secretary Donald H. Rumsfeld. Hayden said he wasn't comfortable with a special Pentagon office set up to study the Iraq intelligence because of the analysis cell's tight focus on what Iraq did wrong, rather than looking at the full picture. The intelligence committee is investigating the office's impact.

Hayden said his concern was whether his uniform would prevent him from bonding with CIA officers. If it gets in the way, he said, "I'll make the right decision."

On the world's hot spots, Hayden acknowledged a series of intelligence failures in the run-up to the U.S. decision to invade Iraq in March 2003, and he promised to take steps to guard against a repeat of such errors.

"We just took too much for granted. We didn't challenge our basic assumptions," he said. The Iraq estimate also focused on weapons of mass destruction and ignored regional or cultural context, he said.

"We're not doing that on Iran," he said. "Besides the technical intelligence, there's a much more complex and harder to develop field of intelligence that has to be applied as well: How are decisions made in that country?"

Hayden said the number of terrorists in the world has grown, but that they are "in capability, much reduced."

Committee Chairman Pat Roberts, R-Kan., complained about the CIA's performance on Iraq: "Nobody bats 1.000 in the intelligence world, but the Iraq WMD failure was due in large part to a terribly flawed tradecraft."

Roberts, a strong Hayden supporter, also expressed regret about the leaks on NSA programs. "I have never seen a program more tightly run and closely scrutinized," he said.

Elsewhere Thursday, BellSouth Corp. called on USA Today to retract claims in its story asserting that the telecommunications company provided phone records of its customers to NSA. Both BellSouth and Verizon Communications Inc., another company cited in the story, denied this week that they provided the calling records.

USA Today spokesman Steve Anderson said the newspaper has not made any decisions regarding action it might take.

The White House hopes the Senate could approve Hayden as soon as next week, enabling him to step in as Porter Goss departs on May 26. Even with the tough questioning, Hayden appeared likely to be confirmed in the Republican-controlled Senate.