Russian warplanes had carried out air strikes against militants it held responsible for firing shells filled with chlorine gas at the city of Aleppo
International investigators on Tuesday entered a Syrian town hit by an alleged chemical attack.
U.S. accused Russia on Monday of blocking international inspectors from reaching the site of a suspected poison gas attack in Syria
Iran's Foreign Ministry said reports of a gas attack in Syria were an "an excuse" by the United States to take military action against Damascus
The U.S. is "extremely concerned" about reports that Syrian forces recently used chlorine gas as a weapon in attacks in the eastern Ghouta area of Syria.