The UN's envoy for the Syrian crisis has offered to personally escort hundreds of al-Qaeda fighters out of Aleppo if it would end hostilities.
Staffan de Mistura, the 69-year-old Italian aristocrat, warned that if the fighting continued the city would be completely destroyed by Christmas and hundreds of thousands of refugees would be fleeing its remains.
Speaking in Geneva, he said about 900 members of Jabhat al-Nusra, an al-Qaeda-linked group, were still there.
"A thousand of you are deciding on the destiny of 275,000 civilians," he said. "If you did decide to leave with dignity and with your weapons, to Idlib or anywhere you wanted to go, I personally am ready physically to accompany you. I can't guarantee more than my own body."
Mr de Mistura also addressed the Syrian and Russian governments, asking them to agree to an "immediate and total aerial bombardment halt [of Aleppo] if al-Nusra leaves".
Sergei Lavrov, Russia's foreign minister, said Russia was interested in Mr de Mistura's proposal and would study it. It was not clear what the Assad regime made of the idea.
There was also no response from al-Nusra itself but analysts, rebel groups and civilians denounced the offer for essentially accepting the regime's premise that it was fighting terrorism.
"No one helped Assad and Russia more than de Mistura," said Abdelkafe al-Hamdo, an English teacher and activist in east Aleppo. "De Mistura is now a partner in killing children, women and all civilians inside Aleppo."
Mr de Mistura made his offer as Syrian regime troops, backed by Iranian, Iraqi and Hizbollah fighters, pressed further into east Aleppo. The regime had earlier warned civilians to flee or meet their "inevitable fate".
In Moscow, the ministry of defence warned that Russian forces could shoot down coalition jets if the US launches airstrikes against Assad. US officials have reportedly discussed using limited airstrikes to force Bashar al-Assad's government to halt its assault on Aleppo and return to the negotiating table after a ceasefire collapsed last month.
US military planners should "carefully consider the possible consequences" of such action, Major General Igor Konashenkov said yesterday.