"That's the key," Lieberman said on "CBS This Morning," adding that he'd set up safe zones to allow the rebels to fight. "It would really help tip the military balance on the ground and bring the conflict to a quicker end."
Lieberman, who is a member of the Senate Armed Services Committee, said he doesn't want to see American troops on the ground but would "leave open the option" of flying American planes over Syria to prevent Assad from aerial attacks.
"This is a desperate man who gives every indication of holding on so long he may destroy his country," Lieberman said of the concern that Assad could use chemical weapons against his people.
Turning to American politics, Lieberman told co-hosts Charlie Rose and Gayle King that Romney's running mate should be someone who can be an effective president and who can help the nominee get elected.
"If you only go for someone who has political appeal, then you made the wrong choice," said Lieberman, who was Al Gore's nominee in 2000.
"The presidential nominee's choice of a running mate is one of the most singular, unilateral exercises power in American politics," he added.