|A damaged field hospital room is seen after airstrikes in a rebel held area in Aleppo. REUTERS/Abdalrhman Ismail
The confirmation that the U.S.-Russian talks on Syria have collapsed suggests that there is little hope, if any, of a diplomatic solution emerging anytime soon to end a 5-1/2-year-old civil war that has killed hundreds of thousands of people and displaced 11 million.
"The United States is suspending its participation in bilateral channels with Russia that were established to sustain the cessation of hostilities," U.S. State Department spokesman John Kirby said in a statement.
Secretary of State John Kerry last spoke to his Russian counterpart, Sergei Lavrov, on October 1, a senior State Department official said, after Kerry threatened last week to walk away from the talks.
In Moscow, Foreign Ministry spokeswoman Maria Zakharova told Russian news agencies the United States was trying to shift blame onto Russia, which in recent days had tried to sustain the agreement.
But Syrian President Bashar al-Assad's forces, supported by Iranian-backed militia and Russian air power, have since last week stepped up their offensive against rebel-held areas of Aleppo, Syria's biggest city, bombing hospitals and damaging water supplies.
In the northeastern city of Hasaka, a bomb killed at least 20 people at a Kurdish wedding, according to a Kurdish militia and a monitoring group.
A U.S. intelligence official said the bombing campaign was "one of the deadliest" since the civil war erupted in 2011.
"These air strikes, mostly focused on Aleppo, have utilized a wide variety of deadly munitions, including barrel bombs, thermobaric bombs, incendiary munitions, cluster bombs and bunker busters," the official said, speaking on condition of anonymity.
The end of the talks could trigger deeper U.S. consideration of military options such as providing more sophisticated arms, logistical support, and training to Syrian rebel groups, either directly or via Gulf Arab states or Turkey.
But the speed with which the ceasefire collapsed - after a U.N. aid convoy was bombed in Syria - appeared to take some officials in the Obama administration by surprise and without a clear plan on the immediate way forward.