More than 100 U.S. troops began conducting live-fire exercises near a U.S. base in southern Syria following Russian threats on the area.
Russia sent the U.S. two messages warning that it planned to attack "terrorists" in the same area as At Tanf, where U.S.-led coalition forces are garrisoned in the fight against ISIS.
U.S. Command has rejected Russia's plans to strike purported terrorists there, saying it doesn't want to fight but "will not hesitate" to use force to defend U.S. or allied forces.
On Friday, the U.S. began the live-fire exercises in the region. Unnamed U.S. defense officials told CNN the hope is that this will cause Russia to back off.
Tensions are mounting in Syria. Russian and Syrian government forces have been bombing parts of northern Syria's Idlib province, one of the last rebel strongholds. U.S. officials warned an all-out assault on Idlib would have "dire" consequences.
Additional reporting by Newsy affiliate CNN.