The US and Russia say world powers will meet in New York on Friday to pass a UN resolution endorsing the Syria peace process.
It follows talks in Moscow between US Secretary of State John Kerry, his Russian counterpart Sergei Lavrov and President Vladimir Putin.
Mr Lavrov said both sides would keep working on contentious issues, like the make-up of the opposition delegation.
Mr Kerry said they had reached some agreement, such as on terrorist groups.
Russia launched an air campaign to bolster Mr Assad's government in September. It says it has targeted only "terrorists", above all jihadist militants from the Islamic State (IS) group, but activists say its strikes have mainly hit Western-backed rebel groups.
Friday's meeting in New York would pass a UN resolution reaffirming the principles of the peace process agreed in Vienna last month, Mr Lavrov said.
Mr Kerry travelled to Moscow to try to bridge gaps over ways to end the Syrian conflict.
He told President Putin the two countries had "the ability to make a significant difference".
The US and Russia disagree on what role Syrian President Bashar al-Assad should play in any transition.
The US wants him to stand down, but Russia says only the Syrian people should decide his fate.
BBC: Syria conflict: US and Russia signal new push at UN (1)