Statement by the Press Secretary on Syria
The United States has identified potential preparations for another chemical weapons attack by the Assad regime that would likely result in the mass murder of civilians, including innocent children. The activities are similar to preparations the regime made before its April 4, 2017 chemical weapons attack.
As we have previously stated, the United States is in Syria to eliminate the Islamic State of Iraq and Syria. If, however, Mr. Assad conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price.
Sean Spicer, Statement by the Press Secretary on Syria Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/329465