Brennan has been the administration's chief architect of so-called targeted killings and deadly drone strikes against al-Qaida militants, including U.S.-born Anwar al-Awlaki in Yemen.
"We only take such actions to save lives when there is no other alternative to mitigate that threat," Brennan said, adding officials agonize over trying to limit dangers to civilians.
Brennan said the United States remains "at war with al-Qaida and its associated forces."
Sen. Ron Wyden, D-Ore., said the drone program includes "unfettered power without checks and balances that is so troubling." Wyden said the U.S. Justice Department had not been following through with delivering the documents on the program that the committee had requested, and Obama had committed to providing.
Wyden asked Brennan to see what he could do to provide the documents.
Brennan also told the Senate Select Intelligence Committee, which is considering his nomination, the United States is under "daily cyberattack by nation states" and individual hackers.
Panetta: More diplomatic security in works
WASHINGTON, Feb. 7 (UPI) -- Defense Secretary Leon Panetta told Congress Thursday security is being stepped up at U.S. diplomatic facilities overseas.
Panetta told the Senate Armed Services Committee plans call for adding 35 new Marine security guard contingents during the next two or three years, The New York Times reported.
"We are working with [the State Department] now to identify specific locations for the new detachments," Panetta said during a hearing on the Sept. 11, 2012, attack on a U.S. diplomatic facility in Benghazi, Libya, in which U.S. Ambassador to Libya Christopher Stevens and three other Americans were killed.
Although Marine security detachments are in place at 152 diplomatic facilities around the world, none was stationed at the Benghazi facility when it was besieged in what the Obama administration has characterized as a terrorist attack.
Panetta told the Senate committee the U.S. military did not have advance intelligence indicating an assault in Benghazi was imminent and no U.S. forces were close enough to Benghazi to be sent there quickly once the attack began.
Tunisia's ruling party rejects P.M.'s plan
TUNIS, Tunisia, Feb. 7 (UPI) -- Tunisia's governing Ennahda Party rejected its leader's call for a unity government Thursday, the day after the assassination of an opposition leader.
Prime Minister Hamadi Jebali urged the dissolution of his government Wednesday, The New York Times reported. Abelhamid Jelassi, the Ennahda vice president, responded with a statement on its website.
"The prime minister did not ask the opinion of his party," he said. Jelassi, Ennahda's vice president, said in a statement reported on the party's Web site and Tunisian news reports. "We in Ennahda believe Tunisia needs a political government now. We will continue discussions with other parties about forming a coalition government."
Chokri Belaid, 48, a leading opposition leader and government critic, was shot and killed outside of his home in Tunis Wednesday. Belaid, general secretary of the Democratic Patriotic Party, was shot as he was leaving his house.
In Tunis, residents told the Times the crowds on the streets were much smaller Thursday than they had been in the hours after the assassination. But the capital remained tense, and French diplomats said embassy schools in Tunis would be closed for the rest of the week.
Search for ex-cop suspected in 3 slayings
IRVINE, Calif., Feb. 7 (UPI) -- Police in Southern California said a former Los Angeles police officer suspected of killing three people was spotted in the San Diego area Thursday.
The suspect, Christopher Jordan Dorner, 33, published a manifesto online, in which he threatened to harm police officials and their families, the Los Angeles Times reported.
A manhunt was under way for Dorner, suspected of the weekend killing a young Irvine couple and a Riverside police officer.
Officials said one LAPD officer was wounded in the Corona area Thursday. Two Riverside police officers were shot in Riverside, one fatally, law enforcement sources said.
San Diego police Capt. Terry McManus told a news conference there is evidence "that is clear to us indicates Dorner was in the San Diego area."
Los Angeles police Chief Charlie Beck told reporters Thursday the situation was "extremely worrisome and scary," and said Dorner, a former U.S. Naval Reserve lieutenant, was "armed and extremely dangerous," the Los Angeles Times reported.
Safety regulator chides FAA
WASHINGTON, Feb. 7 (UPI) -- A U.S. safety official said the Federal Aviation Administration needs to rethink how it certifies batteries such as those used in the grounded 787 Dreamliner.
"The assumptions used to certify the batteries must be reconsidered," said Deborah Hersman, chairwoman of the National Transportation Safety Board.
Two fires aboard the new Boeing jets triggered the grounding of the 50 jets in commercial use after less than 100,000 hours of commercial flights, The New York Times reported Thursday.
The time element is significant, as Boeing had said in its certification application that the lithium ion batteries used in the jet -- and the source of the recent fires -- could be the source of a fire incident fewer than once in every 10 million hours of use.
Hersman said the investigation of the batteries "has demonstrated that a short-circuit in a single [battery] cell can propagate to adjacent cells and result in a fire." What is unknown, however, is what caused the short circuit in the single cell in the first place.