Syrian regime forces made rapid inroads in eastern Aleppo Tuesday, as government ally Russia accused the United States of cancelling a key meeting to discuss the fate of the shrinking rebel enclave.
Opposition fighters who refused to leave the area would be "eradicated," Russian Foreign Minister Sergei Lavrov said in remarks carried by Russian state news agency TASS.
Government forces captured the al-Shaar district and a number of adjoining areas, confining rebels to the southern part of the enclave, the Syrian Observatory for Human Rights said.
Locals said al-Shaar had been abandoned by residents ahead of the advance of government forces, who have captured over two thirds of eastern Aleppo in the last two weeks.
Syrian state news agency SANA said that government forces had also captured the adjoining Qaterji district and the Merjeh and Sheikh Lutfi areas further south.
Observatory director Rami Abdel-Rahman said those areas had not yet fallen, but parts of them were exposed to the regime's firepower.
Lavrov meanwhile said the US had "changed their mind" and cancelled a meeting to discuss the fate of the enclave.
The US had sent Russia a new proposal that "takes everything back to square one and looks like an attempt to gain time to let militants take a break and replenish their reserves," he charged.
Countering the Russian claims, US State Department spokesman Mark Toner said in Washington that, "talks haven't been cancelled. We never were in a position to confirm that these talks were taking place this week."
He added that "we're still pursuing those, we're just not in a position yet where it [makes] sense for us to meet. That's all it is."
A member of the opposition Syrian National Coalition placed the blame on Russia, accusing it of attempting to break off the peace talks and adopt "escalatory measures."
Russia wants the rebels to leave, "but they also want the remaining civilians to leave as well," Ahmed Ramadan told dpa.
US Secretary of State John Kerry told reporters in Brussels that "there may or may not be a meeting this week," but that Russia should bring Syrian President Bashar al-Assad to future Syria peace talks.
"Russia says that Assad is prepared to come to the table," Kerry told reporters in Brussels. "They say that's part of their agreement and they would support it, that he has to engage in good faith in the negotiating process."
"I am personally deeply in favour of putting that to the test," Kerry says.
Moscow and Iran are the main military backers of the Syrian government, while the US supports the political opposition and has given limited support to some rebel groups.
Lavrov vowed that rebels who refused to leave eastern Aleppo "will be eradicated. There is no other solution."
The fall of eastern Aleppo, the only major urban centre still in rebel hands, would be a major blow to the opposition, freeing government forces up for deployment elsewhere and strengthening President Bashar al-Assad's claim to power.
As fighting continued in Aleppo, towns and villages in rebel-held Idlib province south-west of the city again came under heavy airstrikes while rebels shelled a regime-held enclave in the area.
At least 25 people were killed in what appeared to be Russian air raids on the province, the observatory said, bringing the total dead in airstrikes on the region to 121 over the last 72 hours.
The strikes on Idlib have killed more than 300 people, including some 100 children, since mid-November, according to the monitoring group.
Meanwhile, at least 12 people were killed in the third day of shelling on the regime-held Shiite villages of Kefraya and Fouaa near Idlib city, the observatory reported.
Rebels have been besieging the villages since early 2015 and regularly shell them, apparently in retaliation for government attacks on rebel-held areas.
Idlib and adjoining districts make up the largest remaining rebel-held zone in Syria, and have repeatedly been hit by airstrikes that have devastated civilian infrastructure including hospitals.
