"There could be no military solution to the Syrian conflict and it can only end through a negotiated political process.
"[They] reaffirmed their determination to continue active cooperation with a view to advancing the political process consistent with the decisions of the Syrian National Dialogue Congress in Sochi and the UN Security Council Resolution 2254," the statement said.
The leaders expressed their "satisfaction with the achievements" of the Astana format since January 2017, in particular, the progress made in "reducing violence across the Syrian Arab Republic and contributing to peace, security, and stability in the country."
Iran, Turkey and Russia "emphasized strong and continued the commitment to the sovereignty, independence, unity and territorial integrity of Syria, as well as to the purposes and principles of the UN Charter and highlighted that they should be respected by all."
The leaders "rejected all attempts to create new realities on the ground under the pretext of combating terrorism," while expressing determination to stand against separatist agendas aimed at undermining the sovereignty and territorial integrity of Syria and national security of neighboring countries."
The joint statement said the leaders highlighted the "need to create conditions for the safe and voluntary return of refugees and internally displaced persons (IDPs) to their original places of residence in Syria."
Russia, Iran, and Turkey also called for the United Nations and its humanitarian agencies to help Syria by providing additional humanitarian aid.
The joint statement also welcomed the progress in the work of the Working Group on the release of detainees and abductees, and handover of the bodies as well as the identification of the missing persons, as undertaken with the participation of the UN and ICRC experts.
The next tripartite meeting will be held in Russia, upon the invitation of President Putin.