Cooperation with Fateh al-Sham, formerly al-Qaeda's Nusra Front, could bring "dire consequences" for Syria's mainstream rebel groups once a proposed US-Russian deal to attack hardline Islamist militants comes into effect, Washington's envoy to Syria is warning.
In a letter to armed opposition groups seen by Reuters, Michael Ratney urged them to abide by the US-Russian deal, saying it gave them the right of self-defence against attacks by the Syrian army and Russia.
He said the deal would end aerial bombardment by Russia and the Syrian air force of their positions and of civilians living in areas they control.
