Russia and the US have discussed possible cooperation to defeat terrorist groups in Syria.
The phone call between the US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov also covered deliveries of humanitarian aid and a resolution to the Syrian conflict.
Kerry and Lavrov were scheduled to meet in Geneva in the next 24 hours but its unclear whether the rendez-vous will go ahead. The Kremlin said movement was needed on a small number of issues.
“We said and repeated multiple times what is in our view the main hindrance. It is the question of separating moderate opposition from the terrorists. This is the core problem now, and I cannot give you further details,” explained Foreign Ministry spokesperson Maria Zakharova.
As talks stall between the US and Russia, the Syrian opposition presented a peace plan in London.
On Wednesday, the roadmap for a transition in the war-ravaged country called for a six-month negotiation between the regime and the opposition, followed by an 18-month period to set up a transitional government and the departure of President Bashar al-Assad.