In testimony before the Senate Armed Services Committee, Mullen, who would replace Marine Gen. Peter Pace, warned strife in the Arab and Islamic worlds "bear directly on the safety of the United States."
"I'm especially concerned about the increasingly hostile role played by Iran," Mullen said. "I support diplomatic efforts to counter Iran's destabilizing behavior and hope their leaders will choose to act responsibly, but I find their support for terrorism and their nuclear ambitions deeply troubling."
Saying Iraq "weighs heavily" on his mind, Mullen said he believes the U.S. troop surge is doing what it is supposed to do, giving commanders the forces they need to improve security and the government of Iraq breathing space.
Selena Gomez drops F-bomb, walks off stage during Jingle Ball performance
'SNL': 'Anchorman 2' cast, One Direction sing 'Afternoon Delight' [VIDEO]