President Obama's counterterrorism chief says Al Qaeda is in decline but revealed that the administration's new counterterrorism strategy is refocused on the group's recruiting capabilities around the world as the Middle East landscape evolves.

"It's true that these changes may bring new challenges and uncertainty in the short-term, as we are seeing in Yemen," the president's chief counterterrorism adviser John Brennan said in a speech Wednesday. "It also is true that terrorism organizations and nations that support them will seek to capitalize on the instability that change can sometimes bring."

Brennan added that U.S. efforts aimed at Al Qaeda, coupled with regional instability have limited the terror organization's potential in planning high-profile attacks and thus, U.S. focus is changing in the new strategy.

"Our strategy is also shaped by a deeper understanding of al Qaida's goals, strategy, and tactics," he said. "I'm not talking about al Qaida's grandiose vision of global domination through a violent Islamic caliphate. That vision is absurd, and we are not going to organize our counterterrorism policies against a feckless delusion that is never going to happen."

The damage done to Al Qaeda's core leadership is mostly responsible for allaying the fears of a large-scale attack. Brennan says almost every Al Qaeda affiliate has lost a major leader in the last few years.

"Yes, al Qaida is adaptive and resilient and has sought to replace these leaders, but it has been forced to do so with less experienced individuals," he said.

That opens up the possibility of smaller, more targeted attacks. Brennan says the new plan takes into account that the federal government simply can't stop every single person who seeks to attack America.

"A responsible, effective counterterrorism strategy recognizes that no nation, no matter how powerful -- including a free and open society of 300 million Americans -- can prevent every single threat from every single individual who wishes to do us harm," he said.

That also raises the fear that potential terrorists already in the U.S. could act out individually since there is an Al Qaeda leadership vacuum.

But he added the killing of Usama Bin Laden has been "the biggest blow against Al Qaeda yet," and that it is possible the group "is in disarray at the highest levels."

While the new strategy generally responds to a more scattered enemy, it says specifically Iran, Syria, Hezbollah and HAMAS support terrorism as a weapon against the U.S.

Fox News Justice producer Mike Levine contributed to this story.