The four leaders "underlined their firm conviction that there could be no military solution […] and that the conflict could be resolved only through a negotiated political process," the statement read.
Presidents Vladimir Putin of Russia, Recep Tayyip Erdogan of Turkey, Emmanuel Macron of France and Chancellor Angela Merkel of Germany met in Istanbul to review developments in Syria.
They further emphasized the need to increase coordination among all international initiatives which aim at contributing to a credible and sustainable solution to the Syrian conflict.
On terrorism, the four leaders "expressed their shared concern on the risks and threats emanating from the conflict for regional as well as global security and stability."
The leaders observed that they were determined to "fight against terrorism in Syria in order to ultimately eliminate" Daesh and the Nusra Front, as well as other groups linked to Daesh or Al-Qaeda. On the demilitarized zone in Idlib, they welcomed the September memorandum between Turkey and Russia to establish a buffer zone and "commended the progress in terms of withdrawal of heavy weapons as well as radical groups."
The leaders reiterated their "strongest opposition to the use of chemical weapons by any party" in Syria, and called for strict compliance with all relevant conventions.
On the constitutional committee, the four said that it should convene in Geneva by the end of the year to pave the way for free and fair elections under UN supervision and with the participation of all diasporas.
The statement called for more confidence-building measures, including the release of detainees and a handover of political prisoners, also demanding that aid agencies receive rapid access throughout the war-torn nation.
The joint communique "highlighted the need to create conditions throughout the country for the safe and voluntary return of refugees," and commended host countries for their efforts.
The four leaders "expressed their commitment to working together in order to create conditions for peace and stability in Syria, encourage a political solution and strengthen international consensus in that regard."