Russian President Vladimir Putin arrived in Tehran on Friday for a meeting with his Iranian and Turkish counterparts to discuss Syria, the Iranian Students' News Agency (ISNA) reported.
Russia and Iran have given military aid to Syrian President Bashar al-Assad in the country's seven-year-old conflict while Turkey has backed rebel forces.
The leaders are scheduled to discuss the looming military assault on Idlib in northwestern Syria, the last major stronghold of active opposition to Assad's rule.