The truce came into force in Aleppo at 12:01 am on Wednesday, the US State Department spokesperson Mark Toner said in a statement on Wednesday.
“We have seen an overall decrease in violence in these areas, even though there have been reports of continued fighting in some locations,” he said.
“Our objective remains, and has always been, a single nationwide cessation of hostilities covering all of Syria – not a series of local truces,” Toner added.
Russian Foreign Minister Sergey Lavrov said that the Russian and US militaries discussed the Aleppo ceasefire late on Tuesday.
According to UN special envoy Staffan de Mistura, the stalled intra-Syrian peace talks between the government and opposition could be resumed if a ceasefire for Aleppo is agreed upon.
Aleppo, one of Syria’s largest cities, remains a hotspot in the Syrian conflict, with various parts of the city held by different groups.
On Tuesday, a hospital in Aleppo was attacked by a rocket, killing at least three people and injuring more than a dozen, state-run Sana news agency said, adding that women and children were among the casualties. The facility is in an area under the control of government forces, and was targeted by a radical rebel group, according to Sana.