"There is no doubt in my mind that the Russians are responsible, I just don’t know whose aircraft actually dropped the bombs," Dunford testified to the Senate Armed Services Committee.
On Monday, an attack on a UN/SARC convoy carrying humanitarian aid for Syria's Aleppo province killed 20 civilians and an aid worker and destroyed as many as 18 trucks.
Dunford on Thursday admitted that he did not "have the facts," but he repeated accusations from other US officials that two Russian aircraft "were in the area" at the time of the incident.
Additionally, he said Syrian military aircraft were present in the vicinity of the convoy around the time of the attack.
Russia has rebutted claims that its aircraft were around the convoy and explained that Syrian Arab Air Force jets are unable to fly at night when the attack occurred.
The United Nations announced it would suspend aid convoys to Aleppo, but it later said it was prepared to renew activities. According to UN estimates, 2 million people in Aleppo need urgent humanitarian assistance.
