Recep Tayyip Erdogan, the Turkish president - who has compared the PKK to the Islamic State - has said he will only sanction military action if the US agrees to a no-fly zone in the Syrian Kurdish region as a way to form a buffer zone for moderate Syrian rebels to operate in. The US, while also keen to see Mr Assad go, is reluctant to take on that responsibility, as enforcing such a no-fly zone would involve taking on President Assad’s air defence systems.