"The so-called battle for Aleppo… at least proving one thing once again… no military sustainable solution is possible in Aleppo or elsewhere in Syria," de Mistura told reporters.
The United Nations believes the three-hour humanitarian ceasefire windows in Syria, announced by Russia, will be insufficient, Staffan de Mistura added.
On Wednesday, the Russian General Staff said that three-hour humanitarian window with a full cessation of hostilities would be opened every day to ensure safe passage for aid convoys into the Syrian city of Aleppo.
"Regarding the Russian Federation announcement… First of all, we, the UN, were not consulted. Second, based on what we heard from Yacoub El Hillo, our humanitarian coordinator in Damascus, three hours are not enough," de Mistura told reporters.
According to him, the United Nations will maintain the aim for a 48-hour humanitarian ceasefire in Aleppo.
