ANKARA — Any mistake in a planned U.S.-backed operation to drive ISIS from the Iraqi city of Mosul could result in hundreds of thousands of refugees, Turkish presidential spokesman Ibrahim Kalin said on Thursday.

Turkey is locked in an escalating row with Iraq over who should take part in the Mosul assault and Kalin voiced concern that Kurdistan Workers Party (PKK) militants, viewed by Ankara and Western allies as terrorists, could be involved.

The PKK has fought a 32-year insurgency in Turkey, in which more than 40,000 people have been killed, and its leadership is based in the mountains of northern Iraq.

Mosul, home to up to 1.5 million people, has been at the heart of ISIS’ self-declared caliphate in Iraq since 2014. The battle for the city is seen beginning this month.

Turkish soldiers have been training Sunni Muslim and allied Kurdish Peshmerga units at Iraq’s Bashiqa camp, near Mosul, and want them involved in the assault.

But Baghdad’s government objects to the Turkish military presence and wants its own forces at the forefront. Turkey fears the use of Shi’a militias, which Iraqi army units have relied on in the past, will stoke sectarian unrest.

Turkish President Tayyip Erdogan warned Iraq’s prime minister he should “know his limits” after he criticized Turkey’s military presence there and said the Turkish army, shaken by a failed coup bid, had not lost so much standing as to take orders from him.

Al-Abadi has responded on Twitter to Erdoğan.

“We are not your enemy and we will liberate our land through the determination of our men and not by video calls,” Al-Abadi wrote, referring to the Facetime call that Erdogan appeared on during the failed coup.