Russian President Vladimir Putin said Monday that there had been some "alignment" with US counterpart Barack Obama over Syria after talks in China, insisting the two sides could reach a deal soon.

"Despite everything, we have some alignment of positions and an understanding of what we could do to de-escalate the situation in Syria," he told a press conference following the G20 summit in China.

"I believe that we are on the right track and could, at least for some period of time, agree to carry out mutual energetic attempts to make the situation in Syria more healthy," he said.

Putin insisted he believed a deal with Washington could be firmed up in the "coming days" but refused to give concrete details, saying that US and Russian officials are still "working out some of our preliminary agreements."

"We can say that our mutual work with the US in fighting terrorist organisations, including in Syria, will be significantly improved and intensified."

Obama earlier called the talks with Putin on Syria, which lasted about 90 minutes, "productive".

Moscow and Washington support different sides in Syria's festering conflict that has left 290,000 dead, with Russia backing President Bashar al-Assad while the United States supports rebel groups fighting him.

"Both US and Russia are interested in fighting terrorism," Putin said at the conference. "The US President is absolutely sincere in striving for a resolution of the Syrian conflict," also calling the US a "key partner" on security issues.

"I think we managed to get to an understanding of one another and to understanding of the problems that we are facing," Putin added.