US officials say senior al-Qaeda leader Abu Yahya al-Libi was killed in a drone strike in Pakistan on Monday.
US officials said Libi was the target of an attack which hit a volatile tribal area of Pakistan's north-west, killing 15 suspected militants.
There has been no confirmation of his death from sources in Pakistan.
The White House says Libi's death deals a heavy blow to al-Qaeda's operations as he played a critical role in the group's planning against the West.
Washington believes that following Osama Bin Laden's death last year, Libi, an Islamic scholar from Libya, became al-Qaeda's second-in-command after Egyptian-born Ayman al-Zawahiri.
The US does not normally comment on individual drone operations, but this strike came after it emerged in the New York Times that the US president personally approves or vetoes each drone strike.