The US, Russia and other world powers are considering a new plan to set up a ceasefire in Syria within the next four to six months, sources have said.
That would be followed by the formation of a transitional government featuring president Bashar Assad and opposition members. How long Assad could remain in power under the transition is unclear.
Western officials said the US and its partners support the timetable as a first phase towards ending the four-year civil war that has killed more than 250,000 people and uprooted over 11 million.
They said an agreement has not yet been reached but diplomats meeting in Vienna are considering the idea.
As the talks involving foreign ministers and senior representatives of 19 countries were happening, Syrian opposition groups reported that a government missile barrage had killed more than 40 in a Damascus suburb.
The Syrian Observatory for Human Rights and the Local Co-ordination Committees said government forces fired more than 11 missiles at a market in Douma, killing at least 40.
Both organisations and a third Douma-based activist network were reporting dozens more wounded in the mid-morning attack.
The Syrian National Council, the main Western-backed opposition group in exile, blamed Russian air strikes for the “massacre” which it said killed 55 civilians. It said it was the second deadly attack in the past 24 hours after Russian air strikes hit the main hospital in Douma on Thursday.