Syria's army and allies have closed in on areas near Aleppo's Old City, looking closer than ever to achieving their most important victory of the five year civil war by driving rebels out of their last urban stronghold.
Rebels have said they would never abandon Aleppo, after reports that US and Russian diplomats were preparing to meet to discuss the surrender and evacuation of insurgents from territory they have held for years.
Russia said its Syrian government allies had taken control of five more districts of Aleppo, and had now seized 35 districts from the rebels during an advance that has changed the course of the conflict.
The government now appears closer to victory than at any point since 2012, the year after rebels took up arms to overthrow President Bashar al-Assad in a war that has killed hundreds of thousands of people, made more than half of Syrians homeless and created the world's worst refugee crisis.
Govt will not accept Aleppo truce
The Syrian Foreign Ministry said it would accept no truce at this point in Aleppo, should any outside parties try to negotiate one.
Russia and China vetoed a UN Security Council resolution on Monday calling for a week long ceasefire.
Russia said rebels used such pauses in the past to reinforce.
Rebel-held districts of Aleppo, reduced to a few kilometers across, where tens of thousands of civilians are trapped, looks set to fall.
The United Nations, whose staff are restricted to government-controlled areas of the city, described "a very disastrous situation in eastern Aleppo".
"There has been heavy shelling on us, there are massacres (of civilians), there's no electricity and little internet access," said Abu Youssef, a resident of one of the areas still held by the fighters.
The Syrian government and Russia have been calling on rebels to withdraw from the city, disarm and accept safe passage out, a procedure that has been carried out in other areas where rebels abandoned besieged territory in recent months.
Russian Foreign Minister Sergei Lavrov said talks with the United States on the withdrawal of rebels from Aleppo would begin in Geneva this evening or tomorrow morning.
A US official told Reuters they would embrace the talks as a step to save lives.
But rebels have told US officials they will not withdraw, and said there had been no more formal contact with the US administration on the topic since then.
"The Americans asked if we wanted to leave or to stay ... we said this is our city, and we will defend it," Zakaria Malahifji, a Turkish-based official for the Fastaqim rebel group, said.
The Cold War-era superpowers have backed opposing sides in the war, but Russia has intervened far more openly and decisively, joining Iran as well as Iraqi and Lebanese Shia groups to back Mr Assad.
Some of the groups fighting in eastern Aleppo have received support in a US-backed military aid programme to rebels deemed moderate by the West.
However, this has been minimal compared to massive Russian air support to aid Mr Assad's government, which has turned the tide of the war in his favour over the past year.
The army said it had taken over areas to the east of the Old City including al-Shaar, Marja and Karm al-Qaterji, bringing them closer to cutting off another pocket of rebel control.
The British-based Syrian Observatory for Human Rights said al-Shaar and some other areas had been taken, but did not immediately confirm the takeover of all the areas announced by the army.
A Turkish-based rebel official denied al-Shaar had been taken but said fighting continued in the neighbourhood.
'Aleppo a disgrace'
Aleppo, once Syria's commercial and cultural hub, has been a key battleground of the war and suffered some of its worst violence.
German Chancellor Angela Merkel lashed out at the international community's inability to stop the bloodshed.
"Aleppo is a disgrace," she said in a speech to her conservative Christian Democratic Union (CDU) party.
She said world powers must "continue to fight" to establish aid corridors for desperate residents.
The most recent offensive has left more than 341 people dead in east Aleppo, including 44 children, the Observatory says.
Rebel fire into the government-held west of the city has killed 81 people, including 31 children, in the same period, the monitor says.
Tens of thousands of east Aleppo residents have also fled to different parts of the city, including to government-held areas and other rebel neighbourhoods.
Among them is Bana al-Abed, a seven-year-old girl whose Twitter account documenting life in Aleppo has gained international attention.
Concern had grown for the girl and her family after the account went silent for 24 hours but her father told AFP they had fled the fighting and were safe for now.
"The army got really close to our neighbourhood. We fled to another part of east Aleppo and the family is doing well," he said.
