FILE PHOTO: U.S. Secretary of State Rex Tillerson is seen at the Department of State in Washington, U.S. March 28, 2017. REUTERS/Eric Thayer

WASHINGTON (Reuters) - The chemical weapons attack in Syria shows how President Bashar al-Assad operates with “brutal and unabashed barbarism,” U.S. Secretary of State Rex Tillerson said on Tuesday, and called on Russia and Iran to make sure it never happens again.

“Those who defend and support him, including Russia and Iran, should have no illusions about Assad or his intentions,” Tillerson said in a statement. “Anyone who uses chemical weapons to attack his own people shows a fundamental disregard for human decency and must be held accountable.”