"The Secretary made clear the United States and its partners hold Russian Federation responsible for this situation, including the use of incendiary and bunker buster bombs in an urban environment, a drastic escalation that puts civilians at great risk", State Department spokesman John Kirby added. With diplomacy in tatters and a month left to go before USA elections, the Syrian government and its Russian allies are using the time to try and recapture the northern city of Aleppo, mobilizing pro-government militias in the Old City and pressing ahead with the most destructive aerial campaign of the past five years.
WASHINGTON-Secretary of State John Kerry told his Russian counterpart Wednesday that the U.S.is preparing to suspend its engagement with Moscow on Syria if Russia doesn't take "immediate steps" to halt an offensive on Aleppo and restore a cease-fire.
The State Department says Mr Kerry issued the ultimatum in a telephone call to Russian Foreign Minister Sergey Lavrov.
Medical officials say airstrikes have severely damaged two hospitals in eastern rebel-held Aleppo, leading to the death of two seriously ill patients.
"It has become known to us that terrorist groups are preparing to strike Syrian army positions and residential quarters in the eastern part of Aleppo with projectiles loaded with toxic agents as a provocation, in order to put the blame on the government forces", he said.
Aleppo has come under heavy aerial bombardment since the end of a ceasefire a week ago.
Mr Kerry and Mr Lavrov have been leading global efforts to bring the five-year-old civil war to an end, and on September 9 agreed to demand a ceasefire.
She said a U.N. Security Council resolution adopted in May which demands that all parties to conflicts protect staff and facilities treating the wounded and sick has failed to produce any effect on the ground - in Syria or other conflict areas.
Mr Poznikhir said the Russian military received new information about Syrian rebels' involvement in the attack on the convoy, but he did not offer any details.
"Those using ever more destructive weapons know exactly what they are doing - they know they are committing war crimes", he said, in an indirect attack on Syria and Russian Federation.
Another medical centre was struck by artillery fire, killing six people queuing for bread at a nearby bakery.
He said: "I appeal to the conscience of those responsible for the bombardment, who will have to answer before God".
Adham Sahloul, of the Syrian American Medical Society, described the attacks as deliberate.
More than 250 people are believed to have been killed in the besieged city in the last week.
On Tuesday, Syrian government forces liberated most of the al-Farafira district northwest of Aleppo's historic Old City and advanced the frontline for the first time in years.