The Pentagon says the U.S.-led coalition fighting the Islamic State (IS) group has launched a strike against what it describes as pro-government forces in Syria.
It says the June 6 attack occurred after forces supporting Syrian President Bashar al-Assad entered an area near a coalition base in southern Syria with a tank, artillery, antiaircraft weapons, vehicles, and more than 60 fighters.
A statement says the pro-Assad forces ignored several coalition warnings.
The Pentagon statement didn't further identify the targeted forces.
But, in recent weeks, officials have complained about various militants refusing to leave an area near Tanf, Syria.
Washington and its partners train Syrian rebels there to fight IS.
The coalition struck similarly described forces in the area last month.