WASHINGTON — Even as Western nations pleaded for a pause in the fighting in Aleppo to evacuate the wounded, a growing sense of confusion and uncertainty has settled on diplomatic efforts to try to ease the suffering in Syria, fueled by steady Syrian regime advances that saw it retake the old city of rebel-held eastern Aleppo on Dec. 7, as well as the US presidential transition.

Syrian rebel factions asked for a cease-fire in Aleppo Dec. 7, which the regime initially rejected, and were reportedly considering a previously rejected proposal to leave the city.

After days of on-again, off-again signaling between Moscow and Washington, US Secretary of State John Kerry was due to meet with Russian Foreign Minister Sergey Lavrov in Hamburg, Germany, Dec. 7 on a possible US-Russia deal for Aleppo, under which rebel fighters would agree to leave eastern Aleppo, enabling the wounded to be evacuated and humanitarian and medical aid to get in. But adding uncertainty to prospects for an 11th hour US-Russian deal to try to ease the suffering in Aleppo and possibly restart intra-Syrian talks is growing confidence by the Syrian regime that it can achieve an outright military victory in the 5½-year-old conflict, as well as the prospect of a new US administration that favors cooperating with Russia to fight the Islamic State (IS).

US President-elect Donald Trump has spoken frequently of his interest to work with Russia to fight IS, and he suggested he is inclined to cut US support for Syrian rebel groups that oppose Syrian President Bashar al-Assad. By contrast, the outgoing Barack Obama administration, while avoiding direct escalation against the Assad regime and its Russian and Iranian backers, has steadfastly refused to countenance cooperation with the Assad regime and has said it believes he lost the legitimacy to govern Syria given the tens of thousands of his citizens that his regime has killed in the civil war. The Pentagon, under Obama, has also fiercely resisted a now collapsed cease-fire deal, negotiated by Kerry and Lavrov, that called for joint US-Russian targeting of al-Qaeda-linked Syrian militants.