Significant differences remain over the future of Bashar Assad, Philip Hammond has said after talks to end Syria's civil war broke up.
World powers, including Syrian ally Iran, meeting in Vienna agreed to work towards brokering a ceasefire after eight hours of discussions to thrash out ways to tackle the conflict.
It comes as the United States announced it will send in up to 50 members of the special forces to support rebel groups fighting Islamic State (IS) in Syria.
Russia and Iran remain resistant to demands that Assad must go and Mr Hammond said that while the meeting had been "productive", differences remained.
"This is the first time we've had all the protagonists around a table together and that is quite a remarkable achievement in itself," the Foreign Secretary said in Vienna.
"We have discovered over the course of eight hours that actually there is quite a lot that we do agree."
He added: "But we also recognise there are some areas where we have very significant differences. And we have explored some of those differences, most obviously around the future of Bashar Assad.
"We have agreed that our officials will work together to try to narrow those differences and that we will reconvene as a group of ministers within the next two weeks.
"So this is a process now that has some momentum, that will go forward, and that in itself is extremely positive."