"We condemn in the strongest possible terms the Syrian regime's use of chemical weapons," said National Security Council spokesman Ned Price.
A UN-backed investigation found that several units of the Syrian military had used toxic weapons against three villages in northern Syria in 2014 and 2015.
Government helicopters flying from two government-controlled air bases dropped chlorine barrel-bombs on the villages of Qmenas, Talmenes and Sarmin, the panel's latest report said.
Chlorine use as a weapon is banned under the Chemical Weapons Convention, which Syria joined in 2013 under pressure from Russia.
Disclaimer: No Business Standard Journalist was involved in creation of this content