Secretary of Iranian Supreme National Security Council Ali Shamkhani threatened to close all border crossings with Iraqi Kurdistan if it secedes from Baghdad.
Shamkhani told the Islamic Republic News Agency (IRNA):
The separation of Kurdistan Region from Iraq will mark the end of the security and military agreements and will also mark the closure of all border crossings with Iran.
"Iran will work, within the framework of securing its common borders, to re-examine the ways of dealing with the presence of terrorist movements hostile to Tehran in the region. Tehran will take steps which are completely different from those taken before."
Shamkhani added: "The opportunity is still available for the regional officials to respond to initiatives, which aim at securing the interests of the Kurds and Iraq through preventing the establishment of currents that threaten security in the region." He considered the legitimacy of the crossings and border areas between his country and Iraqi Kurdistan as derived only from the existence of Kurdistan within a unified Iraq.
The Kurdish Regional Government will hold a non-binding referendum to determine whether citizens in Erbil, Sulaymaniyah, Dahuk and Kirkuk wish to secede from Iraq. It is due to take place on 25 September.
The Iraqi government, Turkey, Iran, the UN, the US and a number of Western powers have all rejected the referendum and asked the KRG not to hold it claiming it will increase divisions in the country and reduce stability.