U.S. Defense Secretary Leon Panetta says the recent deaths of key al-Qaida leaders make it more difficult for the terror group to carry out large-scale attacks abroad.

Panetta's comments come days after a U.S. drone strike in Yemen killed American-born cleric Anwar al-Awlaki, a key al-Qaida figure, and Samir Khan, a Pakistani-American who produced the terror group's English-language Web magazine, Inspire.

Panetta also told reporters as he traveled to Israel that regardless of whether embattled Yemeni President Ali Abdullah Saleh remains in power, the United States will continue to work with Yemen to counter al-Qaida in the Arabian Peninsula .

The U.S. military has been coordinating with the Central Intelligence Agency and Yemeni authorities to attack AQAP targets, usually with manned aircraft or cruise missiles.

Panetta said he could not confirm whether Friday's airstrike also killed Saudi bomb maker Ibrahim al-Asiri.

The Yemeni government said earlier Sunday that despite reports, al-Asiri was not among the dead.

Al-Asiri is linked to an attempt to blow up a U.S. plane over Detroit on Christmas Day 2009, using a bomb hidden in the underwear of a Nigerian man.