Asked about the possibility of withdrawing all combat troops within two years, Mullen says "the consequences could be very dangerous."
The Joint Chiefs chairman also expressed concern about what he called a "porous border" between Pakistan and Afghanistan allowing al-Qaida and Taliban insurgents to join forces and find safe havens.
On possible fallout from any conflict involving Iran, Mullen says the U.S. is fighting two wars right now and doesn't "need a third one."
