The U.S. is still paying for some small FSA groups within Aleppo city but these are now surrounded by the Syrian Arab Army and unlikely to be able to hold their positions. Their hold of Aleppo city is politically symbolic and therefore something the U.S. wants them to keep. It is the reason why the UN envoy is trying to negotiate a ceasefire for Aleppo. Syria and Russia are playing along but Aleppo will likely be completely in government hands before any ceasefire is reached.