Anwar Al-Awlaki, 40, an influential English-speaking New Mexico-born radical Yemeni cleric, harnessed the Internet to promote violent Jihad. Al-Awlaki's death is the latest in a run of high-profile kills for Washington under Mr. Obama. Al-Awlaki was also linked to a shooting at a US army base. Al-Awlaki was placed on the CIA "kill or capture" list by the Obama administration in April 2010 - the first American to be so targeted.
The strike took place in the morning hours in the eastern Yemeni province of al-Jawf. A second American, Samir Khan, who edited al Qaida's Internet magazine, was also killed in the airstrike.
The officials spoke on condition of anonymity because al-Asiri's death has not officially been confirmed. Christopher Boucek, a scholar who studies Yemen and al Qaida, said al-Asiri was so important to the organization that his death would "overshadow" the news of the deaths of al-Awlaki and Khan.
The voices of Khan and al-Awlaki elevated the several hundred al Qaida fighters hiding out in Yemen into a greater threat than similar affiliates of the terror network in North Africa, Somalia or east Asia.
President Barack Obama heralded the strike as a "major blow to al Qaida's most active operational affiliate," saying the 40-year-old al-Awlaki was the group's "leader of external operations."
Al-Awlaki's death was the biggest success in the Obama administration's intensified campaign to take out al Qaida's leadership since the May killing of Osama bin Laden in Pakistan. At least twice, airstrikes were called in on locations in Yemen where al-Awlaki was suspected of being, but he wasn't harmed.
In July, US Defense Secretary Leon Panetta said al-Awlaki was a priority target alongside Ayman al-Zawahri, bin Laden's successor as the terror network's leader.
Bruce Riedel, a Brookings senior fellow and former CIA officer, cautioned that while al-Awlaki was the "foremost propagandist," for al Qaida's Yemen branch, his death "doesn't really significantly change its fortunes."
al Qaida in the Arabian Peninsula, as the terror branch in Yemen is called, has been operating in Yemen for years, led by a Yemeni militant and former bin Laden aide named Nasser al-Wahishi. Al-Wahishi placed major importance on propaganda efforts.
Al-Awlaki gave the group its international voice.
Hasan initiated the contacts, drawn by al-Awlaki's Internet sermons.
Yemeni officials say they believe al-Awlaki and other al Qaida leaders met with Abdulmutallab in a Yemen hideout in the weeks before the failed bombing. Al-Awlaki has said Abdulmutallab was his "student" but said he never told him to carry out the airline attack.
The FBI questioned al-Awlaki at the time but found no cause to detain him.
In 2004, al-Awlaki returned to Yemen, and in the years that followed, his English-language Internet sermons increasingly turned to denunciations of the United States and calls for jihad, or holy war. Since the Fort Hood attack, he has been on the run alongside al Qaida militants.
US terrorism expert Evan Kohlmann said al-Awlaki's death doesn't affect al Qaida in the Arabian Peninsula's military capabilities. "Al-Awlaki's greatest importance really is a recruiter for homegrown terrorism," he said. The killing of the American cleric Anwar al-Awlaki will instill a "sense of doom" in al-Qaida's surviving leaders, a senior American military official told The New York Times.
The Times reported that the airstrike that killed al-Awlaki and fellow U.S. citizen Samir Khan, 25, was the culmination of a two-year manhunt.
Close calls
Story: Radical American cleric killed in Yemen, officials say
The senior U.S. military official told the Times that the ultimate success of the attempts to kill al-Awlaki would limit the capabilities of al-Qaida.
Story: Plenty of al-Qaida targets remain after Osama bin Laden's death
However, at the Washington-area mosque where al-Awlaki preached a decade ago, there were few tears over his death.
Khalid Abutaa was among those happy to hear the news that al-Awlaki was dead.
Hassan Mohamed, 62, said no allegations against al-Awlaki had been proven.
Video: Second American killed in al-Awlaki strike
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