Iran on Sunday urged an end to a Turkish military offensive in northwestern Syria and called on Ankara to play a "constructive role" in the war-torn country.
Iran "is concerned about and closely watching Turkey's ongoing operation in Syria's Afrin," the foreign ministry said in a statement.
Tehran "hopes that the operation would be immediately terminated so as to prevent the deepening of the crisis in northern Syria," it said.
Turkish troops and tanks entered northern Syria on Sunday in an offensive aimed at ousting the Kurdish Peoples' Protection Units (YPG), which Ankara considers a terror group, from the Afrin region.
Iran and Russia back President Bashar al-Assad, while Turkey supports rebel forces and is keen to prevent the emergence of an autonomous Kurdish region in the country's north
The three powers are joint sponsors of a peace process for Syria that has looked to still fighting by setting up "de-escalation" zones in the country.
The Turkish offensive was launched the same day that Moscow announced the date of a Syrian National Dialogue Congress sponsored by the states backing the Astana process.
The YPG, linked to Turkey's Kurdistan Workers' Party (PKK), has been a key US ally in the war against the Islamic State group, helping to drive the jihadists from swathes of Syrian territory including their stronghold Raqa.
The US-led coalition against IS announced on January 14 it planned to set up a border force in Syria including the YPG, sparking outrage in Ankara.
The United States called Sunday for Turkey to "exercise restraint" and avoid civilian casualties in its cross-border operation targeting Syrian Kurdish forces.
Iran's foreign ministry said Sunday it "expects all countries, especially the Turkish government as one of the guarantor states [of the Astana Process]... to continue to play a constructive role and carry out its responsibility to resolve the crisis in Syria diplomatically."