The Russian side stressed its readiness to consider additional possibilities of normalizing the situation in Aleppo jointly with the US partners, Tass reported.

In response to the (US) Secretary of State’s call to stop the counter terrorism operation in Aleppo with an aim to resume the cessation of military hostilities regime, Lavrov said that the rebels entrenched in the Eastern part of the city, who were controlled by Jebhat al-Nusra [Fatah Al-Sham Front] had violated the truce, which was established by the September 12 Russian-US ceasefire deal, many times.

They are hindering the delivery of relief aid threatening to attack UN convoys, Lavrov added.

It was emphasized that numerous two-day or three-day pauses in fighting which used to be announced in the past had been used by the al-Nusra Front to regroup its forces.

"A week ago, the Russian side urged the United States to live up to its commitment, which Washington undertook as early as in February this year, to separate ‘moderate’ Syrian opposition from terrorist units but that has not been done over the past seven months," the Russian Foreign Ministry said.

The inaction on this thorny issue allows the Jebhat al-Nusra Front to cover itself with armed opposition units with whom Washington cooperates.

But in reality, many of these opposition units have never accepted the Russian-US ceasefire agreements and have practically merged with terrorists.

"The need to make the opposition stop sabotaging the United Nations decision to hold the inter-Syrian talks was re-emphasized once again," the Russian Foreign Ministry said after the Lavrov-Kerry conversation.

Lavrov added that Russia remained open to dialogue with the United States on key problems of the Syrian settlement.