A fresh resolution on a timetable for international control of Syria's chemical weapons is to be presented to the UN Security Council by the US, UK and France.
British prime minister David Cameron announced that following talks between the three countries' leaders they had agreed to draw up a resolution that would set out deadlines for the process of making safe Assad's weapons with consequences if it was not met.
He told a committee of MPs that the Russian initiative appeared to be serious and should be treated as such but with scepticism.
Echoing sentiments already expressed by President Obama, Cameron said: "It is an interesting proposal and, if it's a serious one we should take it seriously.
"I have spoken to President Obama and Britain, France and the US will be tabling a UN Security Council resolution. It is important we have some clarity about thresholds, a timetable and a proper process."
He agreed that the resolution might need to set out "consequences" if deadlines were not met.
"We should be sceptical but this could be a major step forward," he said.
"None of this would be happening if there had not been international pressure, led by the US. We must enter this with a very hard head and some serious calculations."