President Donald Trump said Wednesday a chemical weapons attack in Syria this week that left at least 86 people dead had altered his position on Syria and its leader Bashar al-Assad. Speaking at the White House alongside King Abdullah II of Jordan, Trump called the attack an “affront to humanity” but offered no details about his planned response.

President Donald Trump: “It crossed a lot of lines for me. When you kill innocent children, innocent babies, babies, little babies, with a chemical gas that is so lethal—people were shocked to hear what gas it was—that crosses many, many lines, beyond a red line. Many, many lines.”

When Trump was later asked whether he would consider military intervention in the conflict, he said he would not disclose his plans, leaving open the possibility of a surprise attack.