The U.S. government believes it has killed al Qaeda's chief operating officer, an Egyptian named Mustafa Abu al-Yazid who is also known Sheikh Sa'id al-Masri and also Sheikh Said.

A U.S. counterterrorism official in a position to know said the al Qaeda leader served as a conduit between al Qaeda's top two leaders — Osama bin Laden and Ayman al-Zawahiri — and the organization's various affiliates around the world. Sheik Said was indirectly in contact with Najibullah Zazi, the Afghan immigrant and airport shuttle driver who was arrested and charged last year for plotting to detonate explosives in New York, according to an Associated Press story from October.

"Word is spreading in extremist circles of the death of Sheikh Sa'id al-Masri, widely viewed as the number three figure in al Qaeda," a U.S. counterterrorism official said. "We have strong reason to believe that's true, and that al-Masri was killed recently in Pakistan's tribal areas. In terms of counterterrorism, this would be a big victory. "Al-Masri was the group's chief operating officer, with a hand in everything from finances to operational planning. He was also the organization's prime conduit to Bin Ladin and Zawahiri. He was key to al Qaeda's command and control," the official said

Bill Roggio, the editor of the Long War Journal, reported Monday night that al-Yazid was killed in a drone strike from May 21 that at the time was believed to kill 10 militants.

The United States, in cooperation with Pakistan, stepped up the pace of lethal drone strikes in August 2008 after President Bush signed an executive order giving the commander of Central Command more operational control to order the strikes in ungoverned spaces throughout southeast Asia and the Middle East. Since then, the U.S. intelligence community estimates that at least 15 senior leaders in al Qaeda and the Taliban have been killed in the drone strikes.

"His death would be a major blow to al Qaeda, which in December lost both its internal and external operations chiefs," the U.S. counterterrorism official said. "Though these terrorists remain extremely dangerous and determined to strike at the United States, the removal from the battlefield of top leaders like al-Masri is further proof that the tribal areas are not quite the safe haven al Qaeda and its allies thought them to be."

Mary Habeck, an expert on al Qaeda at Johns Hopkins University's School of Advanced International Studies, said al-Yazid "is not just the number three in al Qaeda, but also one of the original members of the group going back to the 1980s." Ms. Habeck, who also worked in the last administration's national security council, added that al-Yazid has been a leading spokesman for the organization and has in the past issued important public statements defining al Qaeda's mission and strategic priorities.

The 9/11 Commission report described al-Yazid as a financial manager and said he dissented from the 9/11 operation "because he feared the U.S. response to an attack."

In the past, U.S. officials have claimed credit for killing or capturing al Qaeda's number three. In 2005, Abu-Faraj al-Libbi was touted as the al Qaeda number three when he was captured by Pakistani authorities. On Feb. 1, 2008, U.S. officials believed they had killed the al Qaeda number three Abu Laith al-Libi in a drone strike. Khalled Sheik Mohammed, who plotted the 9/11 attacks, has been described by U.S. officials as al Qaeda's number three, as has Said al Adel, an al Qaeda military planner who fled to Iran in 2001 and is believed to have operated in al Qaeda's leadership from the eastern part of the country.