Turkish President Recep Tayyip Erdogan on Saturday condemned the United States' support of Kurdish fighters in Syria after AFP pictures revealed US commandos wearing the insignia of a militia branded a terror group by Ankara.
"The support they give to... the YPG (militia)... I condemn it," said Erdogan. "Those who are our friends, who are with us in Nato... cannot, must not send their soldiers to Syria wearing YPG insignia."
Erdogan's comments came after an AFP photographer captured images of US troops in Syria wearing insignia of the Kurdish People's Protection Units (YPG).
Ankara regards the YPG as a terror group, accusing it of carrying out attacks inside Turkey and being the Syrian branch of the Kurdistan Workers' Party (PKK) which has fought an insurgency against the Turkish state for over three decades.
"The PKK, the PYD, the YPG, Daesh (Islamic State), there is no difference. They are all terrorists," Erdogan said.
It had long been public knowledge that around 200 US commandos are in northern Syria helping local militia target the Islamic State extremist group's de facto capital Raqa and guiding in coalition air strikes.
Erdogan, speaking in the majority Kurdish city Diyarbakir, accused the US of being dishonest because of its support for the militia and its political wing the Democratic Union Party (PYD).
"I believe that politics should be exercised with honesty," he said.
The US. seeking to avoid a rift with ally Turkey, swiftly announced Friday that special operations troops in northern Syria would henceforth stop wearing the badge of the YPG guerrillas.
However the State Department played down the spat, insisting that Washington and Ankara remain close partners in the broader fight against the Islamic State, despite disagreements about the role of the YPG.
Turkish Foreign Minister Mevlut Cavusoglu accused the United States of "hypocrisy" and "double standards" and said the American soldiers might just as well have worn the logo of Al-Qaeda, the IS group or Boko Haram.
The United States has blacklisted the PKK as a "foreign terrorist organisation" but regards its Syrian-based sister group the PYG as a useful ally in the face of the Islamic State threat.
US military officials say they will continue to work with the YPG, which provides the bulk of the so-called "Syrian Democratic Forces" fighting the IS group.