Syrian rebels are in secret talks with Russia to end the fighting in Aleppo, according to opposition figures, a development that shows how the US could become sidelined in some of the Middle East’s most pivotal conflicts.

Four opposition members from rebel-held northern Syria told the Financial Times that Turkey has been brokering talks in Ankara with Moscow, whose military intervention on the side of President Bashar al-Assad has helped turn the five-year civil war in the regime’s favour. Russia is now backing regime efforts to recapture the rebel’s last urban stronghold in Syria’s second city of Aleppo.

“The Russians and Turks are talking without the US now. It [Washington] is completely shut out of these talks, and doesn’t even know what’s going on in Ankara,” said one opposition figure, who asked not to be identified.