Iran has rejected the establishment of Turkish military posts inside of Syria, saying borders between the two countries should be respected.
Speaking at a weekly news conference broadcast on state TV, Foreign Ministry spokesman Abbas Mosavi said issues between Syria and Turkey should be resolved "by diplomatic means."
"We are against Ankara's establishing of military posts in Syria ... Syria's integrity should be respected," he said.
Last week Turkish President Recep Tayyip Erdogan agreed to a temporary halt in fighting to allow Kurdish forces time to pull back from regions under assault in Ankara's military drive to clear a Kurdish-held swath of northeastern Syria.
With an October 22 deadline for the respite to end, Syrian Kurdish militia officials said they were willing to withdraw their forces from a border area in northeastern Syria to comply with the U.S.-brokered cease-fire if Turkish-led forces allow remaining Kurdish forces and civilians to leave an embattled city there.
Turkish Foreign Minister Mevlut Cavusoglu said on October 20 that Ankara does not want "a single Kurdish militant" left in its planned "safe zones" and that Turkey will discuss with Russia, whose forces are fighting in support of Syrian President Bashar al-Assad, the removal of Kurdish militia fighters from the Manbij and Kobani regions of Syria.
Erdogan is scheduled to meet with Russian President Vladimir Putin in the Russian Black Sea resort of Sochi on October 22.
Tens of thousands of civilians have fled cities caught up in the fighting, and many groups fear a humanitarian disaster, particularly as images emerged of apparent abuse and summary executions by Turkish forces.
International outrage at the offensive by NATO member Turkey has been mounting, including from European leaders, who have slapped arms boycotts on Ankara, and U.S. President Donald Trump, who has threatened to "ruin" Turkey's economy if it overstepped.
Trump's October 6 order to remove U.S. troops in northeastern Syria, where they were cooperating with allied Kurdish forces who oppose Assad and had waged an extended battle against IS radicals, was seen by many as green-lighting the Turkish operation.
Critics called Trump's decision a "betrayal" of U.S.-allied Kurds, and many expressed concerns that the thousands of IS prisoners being held by the Kurdish militias would be able to flee during the fighting.
Under the deal declared by U.S. Vice President Mike Pence, all fighting was to halt for five days and the United States was to help facilitate the withdrawal of Kurdish-led troops from a "safe zone" sought by Turkey along the border.
Erdogan has warned that, if the Kurdish withdrawal was not completed by October 22, "we will start where we left off and continue to crush the terrorists' heads."