The United States is weighing a multinational military response to the suspected Syrian poison gas attack, U.S. officials said Monday, as experts listed several key facilities that could be viable targets.

U.S. President Donald Trump promised forceful action on Monday, saying a decision would be made soon following the suspected chemical weapons attack late on Saturday in the Syrian city of Douma that killed at least 60 people and injured more than 1,000 others.

U.S. officials who spoke on condition of anonymity did not disclose any plans, but acknowledged military options were being developed. The White House, Pentagon and State Department declined to comment on specific options or whether military action was likely.