U.S. defense officials believe that Russian planes were responsible for the attack on a humanitarian convoy in Aleppo on Monday.
Officials told Reuters that two Russian Sukhoi SU-24 warplanes were in the skies above the convoy before the attack occurred.
According to the Guardian, at least 20 people, including the local director of the Syrian Arab Red Crescent, were killed when 18 vehicles out of a 31-vehicle convoy were hit by an apparent airstrike by either Syrian or Russian forces.
“There are only three parties that fly in Syria: the coalition, the Russians and the Syrian regime. It was not the coalition. We don’t fly over Aleppo … We would leave it to the Russians and the Syrian regime to explain their actions,” Captain Jeff Davis, a Pentagon spokesperson, said to the Guardian.
During his farewell address to the General Assembly, U.N. Secretary-General Ban Ki-moon, denounced the attack as “sickening, savage and apparently deliberate.”
The U.N. emergency-relief coordinator, Stephen O’Brien, said the attacks amounted to war crimes if the convoy was deliberately targeted.
Moscow has firmly denied involvement in the attacks.
“We are considering, with resentment and indignation, attempts by some foreign curators of rebel units and terrorists in Syria to put the blame for the incident on the Russian and Syrian Aerospace Forces who allegedly bombarded a relief convoy,” said a statement by the Russian Foreign Ministry to the TASS News Agency.
The U.N. later rolled back on claims that the convoy was targeted by an airstrike.
“We are not in a position to determine whether these were in fact airstrikes. We are in a position to say that the convoy was attacked,” U.N spokesperson Jens Laerke told the Guardian.
The strikes have threatened to derail peace talks and came at the end of a one-week truce brokered by U.S. and Russia that was meant to help administer aid to besieged areas.
Reuters reported that after the attack, U.S. Secretary of State John Kerry met his Russian counterpart Sergei Lavrov to discuss the cease-fire before joining a broader meeting of members of the Security Council, the European Union, and Middle Eastern nations to discuss the conflict which has now entered its sixth year.
“The cease-fire is not dead,” Kerry told media.
Not all officials are as optimistic. French Foreign Minister Jean-Marc Ayrault told reporters that “U.S.-Russian negotiation has reached its limits.”