President Trump spoke Monday with Turkish President Recep Tayyip Erdogan, again warning him not to attack U.S.-allied Kurds in Syria after tweeting Sunday he would “devastate Turkey economically” if he did so.

Erdogan stressed during the phone call that he did not oppose ethnic Kurds, but rather the Kurdish People’s Protection Units militia, or YPG, the largest component of the U.S.-allied Syrian Democratic Forces, according to a Turkish government statement.