The US and Russia have agreed to aim for a draft version of a new constitution for Syria by August, US Secretary of State John Kerry has said, the BBC reports.
Mr Kerry was speaking after four hours of talks at the Kremlin with Russian President Vladimir Putin.
He said they also agreed to press the Syrian government and rebels to speed up talks on a political transition.
A round of indirect peace talks in Geneva between the Syrian government and opposition concluded on Thursday.
UN envoy Staffan de Mistura said he had found a lot of common ground between the two sides.