A CIA drone strike has targeted al Qaida's second in command, Abu Yahia al-Libi, in Pakistan, but it is unclear whether he was hit, US officials said.
Fewer than five people were hit in two days of strikes in Pakistan during a period of half a dozen strikes in less than two weeks, as America pushed ahead with the controversial drone programme despite Pakistani demands that it stop.
US officials said they did not know yet whether al-Libi was among those killed, but said they were "optimistic".
The Libyan militant, as his name implies, would be the latest in the dozen-plus senior commanders removed in the clandestine US war against al Qaida since navy SEALs killed Osama bin Laden last year.
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 programme had set a million-dollar reward for information leading to the Libyan-born fugitive, who had filmed numerous propaganda videos urging attacks on US 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 bolster the CIA's push to continue the drone programme 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 the Brookings Institute's Bruce Riedel, a former CIA officer and adviser to the White House on Afghanistan and Pakistan policy.