President Bush is expected to nominate General Michael Hayden as the next CIA director during a formal announcement on Monday morning, FOX News has learned.

Hayden, known as someone willing to do battle in defense of the positions he holds, may need that quality as the 61-year-old Air Force general goes up against a leery Senate tasked with confirming a new CIA chief.

Sen. Arlen Specter, R-Pa., the Judiciary Committee chairman, told "FOX News Sunday" that the Senate may use its role in the nomination process as "leverage" to learn more about the president's decision to allow the National Security Agency to conduct warrantless wiretaps of people in the United States who had conversations with suspected terrorists abroad.

Hayden was head of the NSA at the time of the wiretapping of international calls and e-mails. The New York Times disclosed the program in December, triggering an uproar over its legality.

"Senator Specter and I, with his lead, have been trying to figure out what Hayden has actually been doing in those wiretaps, and it may give us an opportunity to figure out what the program actually is," said Sen. Joe Biden, D-Del.

But since the program's exposure, Hayden hasn't backed off defending the surveillance.

"These are communications that we have reason to believe are Al Qaeda communications, a judgment made by American intelligence professionals, not folks like me or political appointees," he said in a speech at the National Press Club right after the story broke.

"So let me make this clear. When you're talking to your daughter at state college, this program cannot intercept your conversations. And when she takes a semester abroad to complete her Arabic studies, this program will not intercept your communications," Hayden said.

Hayden ran the super-secret NSA from 1999 until last year, when he became the top deputy to the new national intelligence director, John Negroponte, who oversees the CIA and 15 other intelligence agencies. With his vast authority and close contacts with members of Congress, Hayden has earned critics.

"I think he is part of the White House spin machine on the NSA program," said California Rep. Jane Harman, who has known Hayden for years and is the senior Democrat on the House Intelligence Committee. But, she said, he does an excellent job in his briefings.

Harman said Hayden loves Shakespeare and, with their spouses, attended a play at Washington's Shakespeare Theater.

Hayden had a blue-collar upbringing in Pittsburgh. There was his father's work at a manufacturing company; his brother's employment as a truck driver; Hayden's part-time job as a cabbie to make ends meet after earning bachelor's and master's degrees in history from Duquesne University.

He had Air Force assignments in Bulgaria, South Korea and Germany.

The CIA job opened up Friday, when director Porter Goss resigned in an unexpected announcement from the Oval Office. News of a possible Hayden nomination stirred lawmakers, who suggested in Sunday news shows that the general may not be the best choice for the job.

He would be "the wrong person, the wrong place at the wrong time," said Rep. Pete Hoekstra, R-Mich., chairman of the House Intelligence Committee. Hoekstra said he thinks Hayden is a very capable person, but his history as professional military would cast a dark shadow on the intelligence agency.

"There is ongoing tensions between this premier civilian intelligence agency and DOD as we speak," Hoekstra said, adding that Hayden is inexorably linked to the Department of Defense.

"And I think putting a general in charge — regardless of how good Mike is — ... is going to send the wrong signal through the agency here in Washington but also to our agents in the field around the world," he told "FOX News Sunday."

"You can't have the military control most of the major aspects of intelligence," said Democratic Sen. Dianne Feinstein of California, who is on the Senate Intelligence Committee. The CIA "is a civilian agency and is meant to be a civilian agency," she said on ABC's "This Week."

But Sen. John McCain, R-Ariz., a former Navy pilot, said other military members have been head of the CIA, a position that he called "the toughest job in Washington."

"This is a very important and key post and I hope [lawmakers] will recognize that General Hayden is a very qualified individual and he is the president's selection," McCain said on CBS' "Face the Nation." "General Hayden is more of an intelligence person than he is an Air Force officer."

Hayden has shown he is not likely to shy away from difficult situations.

Matthew Aid, a historian who is writing a book on the NSA, said when a deputy director resisted change at the agency, Hayden sent her to London to fill a liaison job with the British.

Hayden's public defense of the warrantless surveillance program showed his aggressiveness and his ability to dispense with a general's jargon.

Even critics of the surveillance praise his clarity. For them, the problem is in the message.

"He can be an SOB if he wants to be," said Aid, a historian working at the private National Security Archive who is writing a book on the NSA.

Aid said Hayden's transfer of the deputy to London came about because the subordinate was leading the opposition to changing the NSA — from a Cold War agency that intercepted radio communications to one the lives in the world of the Internet and cell phones.

"He didn't say 'You guys are the veterans here, you run the place," Aid said. "He said, 'You're for us or against us. Those who stood with the deputy retired or got kicked sideways."

James Bamford, who has written two books on the NSA, said if Hayden gets the CIA job, he once would again have to overhaul an intelligence agency that has low morale and is trying to find its place in the fight against terrorism.

FOX News' Carl Cameron and The Associated Press contributed to this report.