The United States believes two Russian aircraft attacked an aid convoy near Aleppo in a strike that shattered a one-week truce, U.S. officials said on Tuesday, but Russia denied involvement; Reuters reported.
Despite the military blame game over Monday's deadly attack, diplomats struggled to save the U.S.-Russian ceasefire agreement that took effect on Sept. 12.
The incident, in which 18 trucks from a 31-vehicle convoy were destroyed, looked likely to deal a death blow to diplomatic efforts to halt a civil war now in its sixth year.
Russia's foreign ministry spokeswoman denied the assertion, telling reporters at the United Nations the U.S. administration "has no facts" to support the claim, adding: "We have nothing to do with this situation."
Ben Rhodes, a deputy U.S. national security adviser, said the White House held Russia responsible for what he called an "enormous humanitarian tragedy" but he did not address whether the attack was carried out by Russian aircraft.
Earlier Russia, which denied its aircraft or those of its Syrian government allies were involved, had said it believed the convoy was not struck from the air at all but had caught fire because of some incident on the ground.
The Syrian Red Crescent said the head of one of its local offices and "around 20 civilians" had been killed, although other death tolls differed. The attack prompted the United Nations to suspend all aid shipments into Syria.
Senior officials from 23 nations emerged from a one-hour meeting on Syria at a New York luxury hotel with little more than an agreement to meet again, on Friday, about how to end a conflict that has killed hundreds of thousands and driven millions from their homes.
They also differed on the chances of renewing the ceasefire.
"The ceasefire is not dead," U.S. Secretary of State John Kerry said after the meeting, which he hosted with Russian Foreign Minister Sergei Lavrov.
"Is there still a chance this ceasefire will be effective? I can't answer that question," French Foreign Minister Jean-Marc Ayrault told reporters. He said that without a ceasefire there would be a "spiral of war, but we have to be honest, the U.S.-Russian negotiation has reached its limits."
The U.N. Security Council is due to hold a high-level meeting on Syria on Wednesday.