Russian Foreign Minister Sergei Lavrov said a revival of a ceasefire in Syria depends on all sides involved and not only on "Russia's unilateral concessions".
"One can only speak about the ceasefire revival only on the collective basis," he said in an interview for the TV news show 'Vesti on Saturday'.
Russia and the United States on Sept. 9 agreed to a deal aimed at putting Syria's peace process back on track. It included a nationwide truce, improved humanitarian aid access and the possibility of joint military operations against Islamic State and al Qaeda's Syrian affiliate, formerly known as the Nusra Front.
The truce effectively collapsed after a week when an aid convoy was attacked on Monday, killing some 20 people.
Lavrov called for an investigation of the incident, repeating that Russian or Syrian air forces were not involved in the attack.
He also reiterated his calls for the separation of opposition forces from the Nusra Front, adding that Russia had recently observed that opposition fighters had merged with the Nusra Front.