Russia has said it will carry on bombing rebel-held eastern Aleppo in Syria, defying US demands to stop.
Kremlin spokesman Dmitry Peskov said on Thursday that the Russian air force would continue its support of the Syrian armed forces.
He also urged Washington to deliver on a pledge to separate moderate Syrian opposition fighters from "terrorists".
US Secretary of State John Kerry warned the US was "on the verge" of suspending talks with Russia over Syria.