President Tayyip Erdogan said the United States was trying to create a “Terror Army” on Turkey’s southern frontier by training a Syrian border force that includes a Kurdish militia, and pledged to crush it before it came into being.

The U.S.-led coalition said it was working with the mainly Kurdish YPG-led Syrian democratic forces to set up a new 30,000-strong border force.

The plan has infuriated Turkey, which considers the YPG to be an extension of the PKK, a Kurdish group waging an insurgency in southern turkey and deemed a terrorist organisation by Turkey, the U.S. And the European Union.