Secretary of State John Kerry on Monday laid out the rationale for a U.S. attack on Syria, vowing there would be “consequences” for what he deemed an “undeniable” chemical weapons attack by Syria’s government.

“The president will be making an informed decision about how to respond to this indiscriminate use of chemical weapons,” Kerry said.

“But make no mistake: President Obama believes there must be accountability for those who would use the world’s most heinous weapons against the world’s most vulnerable people.

“Nothing today is more serious, and nothing is receiving more serious scrutiny.”