"Well, I think it's changed. And there's a different landscape out there," Mueller, 69, who is stepping down Sep 4 after 12 years as America's top law enforcement officer, told various American news media.

"After September 11th, you had core Al Qaeda in Pakistan and Afghanistan with (Osama) bin Laden. Bin Laden was killed. You have Al Qaeda growing in countries like Somalia, but most particularly in Yemen," he was quoted as saying by CNN.