Russia has told the United Nations it will stop bombing eastern Aleppo for 11 hours a day for four days, but that is not enough to trigger a wider ceasefire deal under which militants would leave the Syrian warzone, the UN says.
The Syrian military said a unilateral ceasefire backed by Russia had come into force to allow people to leave eastern Aleppo, a move rejected by rebels who say they are preparing a counter-offensive to break the blockade.
"They (the Russians) have said 11 hours per day and four days from today, Thursday," UN Syria humanitarian advisor Jan Egeland told reporters on Thursday. "We hope it can be four days from tomorrow Friday."
"They are considering that additional day," he said, noting that Russia had originally announced an 8-hour pause, but the UN had objected that it was too short to evacuate wounded and bring in assistance.
Russia did not announce the four days of pauses. But its defence ministry said President Vladimir Putin had ordered the first 11-hour pause, which was due to expire on Thursday afternoon, to be extended for a further 24 hours.
Russia has said it stopped bombing because it expects fighters from the banned Jabhat Fateh al-Sham group, previously called the Nusra Front, to leave the city, under a ceasefire deal proposed by UN Syria envoy Staffan de Mistura.
But Mr de Mistura said he regarded the pauses in the bombing as a response to the UN request for medical evacuations.
His ceasefire proposal required more.
"The package is clear, Nusra needs to declare they are ready to go, or others can do on their behalf, and at the same time that there is a commitment by the (Syrian) government to respect the local administration," he said.
"Let's separate the two things. Today we consider this a medical evacuation, or medical support. The next steps are part of a larger package that needs to be there."
Mr Egeland said he hoped the first sick and wounded would be brought out on Friday to government-held western Aleppo or rebel-held Idlib, according to their choice.
"We hope to continue until we have been able to evacuate all of the cases that need such evacuation, and that would be hopefully done in the course of days, and it could be several hundred cases with their families," he said.
UN aid convoys are ready to move from western Aleppo and from Turkey, but there was still no deal to get food into the besieged zone and no guarantee that all would go smoothly.