The Syrian army is calling on the last remaining rebels to leave eastern districts of Aleppo, as the evacuation of their besieged enclave continues.
Soldiers reportedly broadcast messages by loudspeaker on Tuesday, warning that they would soon enter the areas.
But one rebel official said the fighters would only leave once all civilians who wanted to had done so.
The Red Cross says 25,000 people have been evacuated since a ceasefire deal halted the army's offensive a week ago.
It is not known exactly how many are still waiting to leave eastern Aleppo, but the UN special envoy to Syria estimated on Thursday that about 40,000 civilians and 10,000 rebels were there.
Meanwhile, foreign ministers of Syria's key allies Russia and Iran, and Turkey, which backs the rebels, say they will work together to try to end the conflict.
The three parties pledged to jointly guarantee any peace deal between the Syrian government and opposition.
UN Syria envoy Staffan de Mistura has said he wants to reconvene peace talks in Geneva in February. The last round of UN-backed exploratory talks in Geneva, in March 2016, collapsed amid an intensification in fighting.
A Syrian military source told AFP news agency on Tuesday morning that the army was expected to enter the rebel enclave "to clean the area after the fighters leave".
Soldiers, he said, had "issued a call over megaphones to the remaining fighters and civilians who want to leave, to exit the eastern districts".
The military's Facebook account also reported that a "final call" had been made "to the last militants who are inside the districts of east Aleppo to quickly evacuate these districts before the Syrian army enters".
A Turkey-based rebel official told Reuters news agency that only about half of the civilians who wanted to leave had been evacuated so far, and that the remaining fighters would wait for them to go first.
A spokeswoman for the International Committee of the Red Cross, Ingy Sedky, told AFP that "thousands" of people were still waiting to be bussed out.
Fifteen thousand were evacuated on Monday, she said, bringing the total to 25,000.
As part of the ceasefire deal, 750 people have also been evacuated from two predominantly Shia towns in Idlib province that are under siege by rebel forces.
A military media unit run by Lebanon's Shia Islamist Hezbollah movement, which is fighting alongside the Syrian army in Aleppo, reported that another eight buses of evacuees from Foah and Kefraya left at dawn on Tuesday, according to Reuters.
Aleppo was once Syria's largest city, and its commercial and industrial hub before the uprising against President Bashar al-Assad began in 2011.
For much of the past four years it was divided roughly in two, with the government controlling the western half and rebels the east.
Troops finally broke the deadlock this year with the help of Iranian-backed militias and Russian air strikes, reinstating a siege on the east in early September.
After breaking through the rebels' defensive lines in mid-November, they quickly advanced and had seized all but 2.6 sq km (1 sq mile) by the time a ceasefire was brokered by Russia and Turkey, which backs the opposition to Mr Assad.