WASHINGTON – CIA nominee Michael Hayden acknowledged concerns about civil liberties even as he vigorously defended the Bush administration’s wiretapping program as a legal spy tool needed to ensnare terrorists.

Peppered with tough questions at a day-long confirmation hearing yesterday, 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 own place among 15 other spy agencies.

General Hayden spoke of his own concerns about the no-warrant surveillance program and other wiretapping 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.”

General Hayden said he decided to go ahead with the terrorist surveillance program in October 2001 after internal discussions about what more his 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,” General Hayden said. “I could not not do this.”

President Bush selected General Hayden to be the country’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 more about the terror-monitoring work on Wednesday.

General 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?” Senator Levin, a Democrat of Michigan, asked.

“I’m not at liberty to talk about that in open session,” replied General Hayden, currently the country’s No. 2 intelligence official. A closed-door session was planned for the evening.

Republican and Democratic senators alike said they should have been briefed on the work five years ago. More than one said he felt deceived.

“I can’t tell now if you’ve simply said one thing and done another, or whether you have just parsed your words like a lawyer to intentionally mislead the public,” Senator Wyden, a Democrat of Oregon, said. “What’s to say that if you’re confirmed to head the CIA we won’t go through exactly this kind of drill with you over there?”

Senator Feingold, a Democrat of Wisconsin, said he was convinced the program was illegal and questioned whether the phone calls of Americans not linked to Al Qaeda were ever captured. General 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, General 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 September 11, 2001, and the prewar Iraq intelligence. General Hayden, who frequently uses sports metaphors, said he believes American 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.

Some lawmakers questioned whether Mr. 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.

A 37-year Air Force officer, General Hayden tried to show he could disagree with Defense Secretary Rumsfeld. General 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.

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

On the world’s hot spots, General Hayden acknowledged a series of intelligence failures in the run-up to the American decision to invade Iraq and 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?”

General Hayden said the number of terrorists in the world have grown, but “in capability, they are much reduced.”

Committee Chairman Pat Roberts, a Republican of Kansas, 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.”

Mr. Roberts also expressed regret about the leaks on NSA programs. “I have never seen a program more tightly run and closely scrutinized,” he said.

Elsewhere yesterday, BellSouth Corporation 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 Incorporated, another company cited in the story, denied this week that they provided the calling records.

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

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