Iran has threatened to close all borders with Iraqi Kurdistan should the semi-autonomous region proceed with a planned referendum on independence from Iraq.

Iranian news agency Tasnim quoted Ali Shamkhani, a secretary-general of the Iranian national security council, saying that Kurdistan’s separation from Iraq will “end security and military agreements with that region, and is considered a declaration of the closure of all border routes with Iran.”

He said border agreements with the central government in Baghdad would, however, remain in place.

Shamkhani said Iran would “reconsider the method it addresses the existence and movement of terrorist elements in Iraqi Kurdistan which is hostile to the Islamic Republic of Iran, and would take totally different steps,” the agency’s Arabic service quoted him saying.

Iran has been an ardent opponent to the planned independence vote.

Kurdistan Region slated a vote on independence from the central government in Baghdad for September 25, and has, since then, defied calls from Baghdad to postpone the measure.

Baghdad’s government has warned against the move repeatedly, with Prime Minister Haider al-Abadi warning of an army intervention if a “yes” vote results in violence.

Kurdistan gained autonomous governance based on the 2005 constitution, but is still considered a part of Iraq. The region was created in 1970 based on an agreement with the Iraqi government, ending years of conflicts.