The top Republican on the Senate Foreign Relations Committee urged Secretary of State John Kerry Thursday to quickly move forward with a “Plan B” after Syria peace talks collapsed in Geneva Wednesday.

“Now that the cessation of hostilities is effectively dead, it looks like it’s time to consider what Secretary Kerry referred to as a ‘Plan B,’ and I look forward to him laying that out very soon,” Sen. Bob Corker, R-Tenn., said in a statement Thursday. He was referring to the formal ceasefire agreement between the Assad regime, the opposition and other parties hashed out in February.