President Donald Trump says he’ll “forcefully” respond to an alleged chemical weapons attack in Syria.

Trump made the remark in the Cabinet Room of the White House during a meeting Monday evening with his top military leaders, including Defense Secretary Jim Mattis and the chairman of the Joint Chiefs of Staff, Gen. Joseph Dunford.

Officials are trying to determine whether Syrian President Bashar Assad’s government was behind Saturday’s suspected chemical weapons attack on rebel-held Douma, east of Damascus.

Trump says the attack “will be met and it will be met forcefully.”

Trump said earlier that he would soon make a decision on how to respond, and against whom.

READ MORE: What we know about the suspected gas attack in Douma, Syria