Former foreign secretary David Miliband has warned the position of Syrian president Bashar al-Assad is crucial to any long-term settlement after the US and Russia agreed to work together.
Despite this, Miliband, now head of the International Rescue Committee, has expressed cautious optimism about the new Syrian ceasefire plan, which will see hostilities cease for ten days.
He told the BBC: "The indications are certainly that there is a better short-term chance of a decent lull in the fighting than has ever happened before. The degree of Russian engagement seems to be of a much greater order than of any of the previous ceasefire attempts.
"But beyond that, it's going to be a much more tricky enterprise. The great difficulty is going to come down to the future of President Assad.
"The big question is whether or not the big winner of this ceasefire - other than the Syrian people - which is President Assad and his government, whether or not his strength becomes a source for further radicalisation, and further fighting in the medium term, because, obviously, he's been the source of a huge amount of killing, and slaughter across the country, and has radicalised Isis and other groups.
"In the West he is seen as someone who has not just murdered many of his own citizens, but has radicalised those who are still there. On the Russian side they see him as the great hope. And there is nothing in this agreement that gets over that fundamental division at this point.
"If there are enough short-term interests that join the Americans and the Russians, then those of us on the humanitarian side have got a chance to try and make a difference."
In an interview with Julia Hartley-Brewer, journalist Margaret Gilmore highlighted how the ceasefire is not a deterrant to the president.
"It's a very small step towards peace and a real truce" she said. "But President Assad has stated he is determined to recover territory from 'terrorists'.
"You'd have to be a huge optimist to say peace is close by, because it's quite clear these internal problems have not gone away. We're not at the stage of political negotiation yet."