"The factions completely reject any exit - this is surrender," said Zakaria Malahifji, the political officer of the Aleppo-based Fastaqim group.
Al-Farouk Abu Bakr, an Aleppo commander in the powerful Islamist group Ahrar al-Sham, said the rebels would fight on.
"When we took up arms at the start of the revolution to defend our abandoned people we promised God that we would not lay them down until the downfall of this criminal regime," he said, referring to President Bashar al-Assad's government.
"There are no terrorists in Aleppo," he said, speaking from Aleppo. Rebels in eastern Aleppo have consistently said that insurgent groups linked to al Qaeda or inspired by it have no real presence in the opposition-held part of the city.