Russian Deputy Foreign Minister Sergei Ryabkov said on Sunday that Moscow had not reached an agreement with the United States for rebel fighters in Syria's Aleppo to have safe passage out of the city, RIA news agency reported.

Rebel officials told Reuters earlier on Sunday that a proposal had been made by the two countries for fighters to leave the city with their families and other civilians.

"What Western agencies are reporting does not necessarily correspond with reality," Ryabkov said, adding that Russia was working to create the necessary conditions for the safe extraction of people from Aleppo.

"The issue of withdrawing militants is the subject of separate agreements. This agreement has not yet been reached, largely because the United States insists on unacceptable terms," RIA quoted him as saying.

Ryabkov said there was no discussion about a joint proposal with the US on Syria that would then be considered by the opposition. The rebel groups in Aleppo said they had yet to respond to the proposal.

Talks between Russian and US experts will continue in Geneva, he said, adding: "There is some progress, but no agreement."

The Russian-backed Syrian military and its allies have captured swathes of rebel-held eastern Aleppo in a ferocious military campaign, squeezing rebel fighters and tens of thousands of civilians into an ever-shrinking enclave.

The rebel groups in the city have previously said they would not leave eastern Aleppo, while demanding safe passage for civilians who wish to leave for areas to the north of Aleppo near the border with Turkey.

Reuters had reported earlier that a draft of the proposal it received from two rebel officials said the Syrian government and its allies would guarantee that fighters and civilians leaving the city would not be detained or harmed, and would also guarantee the safety of civilians who wished to remain in the city.