Turkish President Recep Tayyip Erdogan today issued an angry condemnation after US envoy to he ISIS War Brett McGurk visited the Syrian Kurdish city of Kobani, asking how he could trust the US while they associate with the “terrorists in Kobani.”

Erdogan went on to warn that the US is ultimately going to have to choose whether its partner is Turkey or the Syrian Kurds. The State Department didn’t directly address this, simply saying they view the Kurdish PKK as “a terrorist organization.”

The US has long said that of the PKK, but is overtly backing the Kurdish YPG in northern Syria. Turkey insists that the two are essentially the same group, and at times Erdogan and other top Turkish leaders have also claimed the PKK and YPG are the same as ISIS.

Erdogan’s government has loudly opposed YPG gains into ISIS territory across northern Syria, and warned they consider the Euphrates River a “red line” which the Kurds must never cross, even though that border area is all controlled by ISIS. The YPG has talked up attacks on this area, and Turkey has threatened to intervene against them.