Fewer than five people were hit in two days of strikes in Pakistan during a period of a half-dozen strikes in less than two weeks, as the U.S. pushed ahead with the controversial drone program despite Pakistani demands to stop. The officials spoke on condition of anonymity to describe the classified drone program.
U.S. officials said they did not know yet whether al-Libi was among those killed, but said they were "optimistic."
The White House maintains a list of terrorist targets to be killed or captured, compiled by the military and the CIA and ultimately approved by the president.
The State Department's Rewards for Justice program had set a $1 million reward for information leading to the Libyan-born fugitive, who had filmed numerous propaganda videos urging attacks on U.S. targets after he escaped a prison at Bagram Air Base in Afghanistan in 2005.
Al-Libi took the second-in-command spot when Egyptian-born Ayman al-Zawahri took charge of al-Qaida after bin Laden's death. As al-Qaida's de facto general manager, al-Libi oversaw the group's day-to-day operations in Pakistan's tribal areas and managed outreach to al-Qaida's regional affiliates.
"This is one of the more prominent names" among the targets of drone strikes in Pakistan, which helps bolsters the CIA's push to continue the drone program despite the continued political resistance from Pakistan and collateral damage, added former CIA officer Paul Pillar.
Al-Libi's death would be "another reason not to accept Pakistan's demand for an end to drone wars," added Brookings Institute's Bruce Riedel, a former CIA officer and adviser to the White House on Afghanistan and Pakistan policy.