ON BOARD A MILITARY AIRCRAFT (AP) ― Defense Secretary Leon Panetta said Monday that the deaths of several top al-Qaida leaders in Pakistan and Yemen in recent months will make it much more difficult for the terror group and its affiliates to plan and launch large-scale attacks abroad, including against the United States.

Panetta said increased cooperation with Yemen against the al-Qaida affiliate there will not diminish if President Ali Abdullah Saleh leaves power as the U.S. and others have urged.

The Pentagon chief spoke to reporters as he was heading to the Middle East, where he is scheduled to meet with top Israeli and Palestinian leaders. After that he will participate in a meeting of NATO defense ministers in Brussels.

Panetta spoke just days after a CIA drone strike killed Anwar al-Awlaki, the American-Yemeni cleric who served as key inspirational leader within the Yemen-based al-Qaida in the Arabian Peninsula.

Killed with him was Samir Khan, a Pakistani-American who produced the group’s English-language Web magazine, Inspire. The strike came a few months after a special operations team raid into Pakistan killed Osama bin Laden.

“By virtue of eliminating that leadership, I think it makes it much more difficult for al-Qaida to develop the kinds of plans and operations for conducting large attacks abroad,” said Panetta.

He added that he does not know if AQAP’s top bomb maker, Ibrahim al-Asiri, was also killed in the strike that targeted al-Awlaki. Officials initially heard al-Asiri may have been killed, but that was later denied by Yemeni authorities.