A U.S. F-16 fighter jet shot down an armed Turkish drone that was operating near American troops in Syria Thursday after several warnings, according to U.S. officials. 

The shootdown came after repeated communications to stay away from U.S. ground troops near al Hasakah, in northeastern Syria.This is believed to be the first time the U.S. has shot down a drone from Turkey, which is a NATO ally. 

Turkey has for the past several days been retaliating against the Kurdistan Workers’ Party (PKK) for a suicide bombing that took place in Ankara Sunday. Turkey considers the Syrian Democratic Forces – who partner with the U.S. in the mission to defeat ISIS – as an arm of the PKK, which it has deemed a terrorist organization. 

There are about 900 U.S. troops operating in Syria as a part of the mission to defeat ISIS. 

The U.S. is holding diplomatic conversations with the Turks.