Russian news agencies, citing Mr Kerry's counterpart Russian Foreign Minister Sergei Lavrov, said Moscow would continue to make efforts to resolve the Syria crisis despite the U.S. suspension of the talks. The official, who spoke on condition of anonymity because he was not authorized to discuss military strategy, refused to say when such an attack might take place.

Speaking in Brussels a day after Washington suspended talks with Moscow aimed at crafting a lasting cease-fire, Kerry said on October 4 that Moscow must ground Russian and Syrian aircraft that are bombing rebel groups and making it impossible to build a lasting truce.

He said that in order to return to the negotiation table, Russian Federation would have to meet global law and fulfil publicly made agreements.

A few days later, on September 19, there was a deadly bombing of a United Nations aid convoy, which the US blames on Russian Federation. The United States and European Union have imposed trade sanctions against Russian Federation since 2014 in protest against Moscow's interference in Ukraine.

Also Monday, the U.N. Security Council began negotiations on a draft resolution seeking an immediate truce in Aleppo and calling for an end to all military flights over the Syrian city.

As part of the decision on Monday, the US will withdraw personnel that had been dispatched in anticipation of the possible establishment of the Joint Implementation Center with Russian Federation.

Russia, an ally of Syria's government, holds veto power along with the United States, France, Britain and China.

The White House and State Department said Monday there was no point to the bilateral discussions any longer because Russia hasn't lived up to a September 9 agreement that included a demand for unfettered humanitarian aid to places like Aleppo, which has been under Russian and Syrian bombardment. The U.S. accused Russian Federation of bombing that convoy, which both Russian Federation and Syria have denied.

Commissioner Zeid has condemned the reported use of weapons such as high-explosive blast bombs and incendiary devices by government forces and Russian Federation in heavily populated areas. "We're trying to make sure black flags won't fly over Damascus", Churkin told reporters at a news conference. It blamed the shelling on two rebel groups, including al Qaeda's affiliate in Syria formerly known as the Nusra Front, but also claimed the attack was the result of a USA policy and that of its allies, which "provokes further bloodshed in Syria".

Putin suspends nuclear deal with US
The Kremlin decree stated that, despite the suspension, Russia's surplus weapons-grade plutonium would not be put to military use. US State Department spokesman John Kirby said in a statement that bilateral contacts with Moscow over Syria were being suspended.

"The Syrian army and its allies are in a sustained offensive to recapture rebel-held eastern Aleppo", wrote Robert Ford, a veteran diplomat and former ambassador to Syria.

The United Nations High Commissioner for Human Rights warned Russian Federation on Tuesday over use of incendiary weapons in air strikes on the Syrian city of Aleppo, where he said attacks on civilian targets may amount to crimes against humanity.

"The regime is bombing civilians because of its inability to storm Aleppo for years", said opposition activist Abu Firas al-Halaby, adding that talk of the imminent arrival of reinforcements was part of a "psychological war" against the rebels. Still, he said government forces will not be able to storm rebel-held neighborhoods of the city.

"Canada denounces the atrocious and ongoing attacks targeting medical facilities in Syria", said Dion, adding that attacks like the one last weekend on Dr. Hasan Al-Araj Hospital "perpetuate suffering and death" and do not help end a crisis he said has lasted far too long. It was the third time the hospital had been hit in a week, including once with several bombs.

Three maintenance workers were killed, he said.

The watchdog said the airstrikes had also killed some 2,746 members of Islamic State of Iraq and Syria (ISIS/ISIL) and 2,814 from other rebel and militant groups.

Dion said Canada supports the USA and the other members of the group "in their tireless efforts to reduce the violence in Syria".

World Health Organization still hopes to be able to evacuate sick and wounded from Aleppo, she said.