BAD RAGAZ, Switzerland (AP) — U.S. Secretary of State John Kerry ramped up already harsh criticism of Syrian President Bashar Assad on Thursday, calling him a “one-man super-magnet for terrorism” who has committed war crimes and could be responsible for the ultimate disintegration of Syria.

Speaking a day after he told an international peace conference that there is no way Assad can play a role in a potential transitional government, Kerry said Assad must act in the best interests of his country and accept that his family’s long reign over Syria is over.