Iran voiced its opposition on Saturday to an announcement by Iraq's autonomous Kurdish region that it will organise a vote on independence later this year.
"Iran's principal position is to support the territorial integrity of Iraq," foreign ministry spokesman Bahram Ghasemi said.
"The Kurdistan region is part of the Iraqi republic and unilateral decisions outside the national and legal framework, especially the Iraqi constitution... can only lead to new problems."
Iraqi Kurdish leaders announced on Wednesday that they will organise an independence referendum on September 25, not only in their three-province autonomous region but also in other historically Kurdish-majority areas they have long sought to incorporate in it.
Iran worries about separatism among its own Kurds, most of whom live in areas along the border with Iraq.
Rebels of the Kurdistan Democratic Party of Iran (KDPI) and the Party of Free Life of Kurdistan (PJAK) launch sporadic attacks into Iran from rear-bases in Iraq, triggering sometimes deadly clashes with the security forces.
After an upsurge attacks in 2011, Iranian troops launched a cross-border incursion, forcing KDPI to retreat deeper into Iraq.
The federal government in Baghdad is deeply opposed to the referendum plan of the regional government in Arbil, as is neighbouring Turkey, which has a large and restive Kurdish minority of its own.
Washington has expressed concern that it could distract from the joint fight against the Islamic State group by stoking tensions between the Kurds, and Arabs and Turkmen in northern Iraq.
"An integrated, stable and democratic Iraq guarantees the interests of the whole people (of Iraq) from all ethnic and religious groups," Ghasemi said.
"Today, Iraq more than ever needs peace and national unity and differences between Arbil and Baghdad must be resolved within the framework of dialogue and in compliance with Iraq's constitution."