Iran's agenda is to expand its borders, and it is openly saying so. Yesterday a high ranking general bragged that Iran is extending its boundaries "from the Red Sea to the Mediterranean." It is a boundary reminiscent of the First Syrian Empire founded by Cyrus the Great in 550 BCE.
The worry is that Eerdogan will go all the way to bond with Russia to which Iran is also attached as a partner. Indeed, Erdogan has scheduled a trip to Tehran a few days after his talks with Putin.