"In my official capacity, I accidentally shared content that was insulting to our Coalition partner Turkey, a key partner in the mission to defeat ISIS. I meant no disrespect," Col. Sean Ryan wrote on Twitter, referring to Daesh.
"We have a duty to mutual security, and we are committed to defeating ISIS. Please accept my apology."
Ryan was referring to a since-deleted retweet of a post classifying as "terrorist" Turkish armed forces.
"US Special Forces (Green Berets) patrolling the Rojava-Turkey border after terrorist Turkish army snipers targeted Rojavan civilians, killing a little girl walking home from school," the tweet said, accompanied by a photograph of U.S. military personnel and children.
The U.S. has been working alongside the YPG-PKK in Syria in its effort to eliminate Daesh from the region.
Turkey views the YPG as the Syrian extension of the PKK, a designated terrorist group in Turkey, the EU and the U.S.