The United States says there are signs the Bashar al-Assad regime in Syria may be using chemical weapons again and it is warning the Syrians to stop it.
The U.S. State Department said Tuesday it believes Syrian forces were behind an alleged chlorine gas attack Sunday in northwestern Syria.
A spokeswoman says officials are still gathering information about the suspected attack but said, "if the Assad regime uses chemical weapons, the United States and our allies will respond quickly and appropriately."
She says the attack would be part of a violent campaign that violates a cease-fire protecting millions of civilians in the Idlib area, destroying health facilities, schools, homes, and refugee camps.
The United States says Syria and its Russian allies have a history of blaming chemical attacks against the rebels.
"The facts are clear: the Assad regime itself has conducted almost all verified chemical weapons attacks that have taken place in Syria ... the Assad regime's culpability in horrific chemical weapons attacks in undeniable."
There has been no comment from Syria on the U.S. accusation.
The U.S. has bombed Syria twice in reaction to using poisonous gas on civilians.