Obama and Putin must act on Syria
It is Barack Obama, the most powerful man in the world, who has the responsibility to end the war in Syria - not Staffan de Mistura of the UN.
Obama has stated that, for peace to come to Syria, America must work with Russia. He seems, however, to have done little (or nothing) towards starting substantive talks with Putin.
David Cameron should be using his influence to get the US and Russia started on a serious peace process.
The refusal to deal with Assad means the Syrian government and army are sidelined as their country is destroyed. It is just not possible to end the chaos in Syria without their involvement.
The US and Russia, with regional allies, can enforce a ceasefire, after which the business of destroying Isil in Syria can begin.