Iraqi prime minister says Kurdistan’s independence referendum is illegal and unconstitutional, and he is prepared to use military force if it escalates.

Iraqi Prime Minister Haider al-Abadi said in an interview that if the Iraqi population is “threatened by the use of force outside the law, then the Army will intervene militarily.”

Speaking in an interview with the Associated Press news agency on Saturday, Abadi said, “If you challenge the constitution and if you challenge the borders of Iraq and the borders of the region, this is a public invitation to the countries in the region to violate Iraqi borders as well, which is a very dangerous escalation.”

The leaders of Iraq’s Kurdish region have said they hope the referendum will push Baghdad to come to the negotiating table and create a path for independence. However, Abadi said such negotiations would likely be complicated by the referendum vote.

“It will make it harder and more difficult,” he said, but added: “I will never close the door to negotiations. Negotiations are always possible.”

Iraq’s Kurdish region plans to hold the referendum on support for independence from Iraq on September 25 in three governorates that make up their autonomous region, and in disputed areas controlled by Kurdish forces but which are claimed by Baghdad.

Iraq’s Kurds have come under increasing pressure to call off the vote from regional powers and the United States, a key ally, as well as Baghdad.