Biden's comments Tuesday make him the highest-ranking U.S. official to say the Syrian regime is the culprit in a large-scale chemical weapons attack on Aug. 21.
Biden says the Syrian government is the only actor in the 2-year civil war that possesses and can deliver chemical weapons. He says Assad has blocked U.N. investigators from the site and has been bombing it for days.
The White House says President Barack Obama hasn't settled on how to respond to the attack. The Pentagon says U.S. military forces are ready to strike Syria if Obama gives the order.
Biden spoke at the American Legion's national convention.