Moves near Azaz in northern Syria by the PKK-affiliated Democratic Union Party's (PYD) armed wing, the People's Protection Units (YPG), including the capture of Menagh Air Base, has discomforted Washington. State Department spokesman Mark Toner said the U.S. urges the YPG to avoid taking actions that will create tensions with Turkey and moderate opposition groups in Syria.

Speaking in his daily briefing on Tuesday, Toner said: "We've been very clear that these moves by the YPG on the ground, we believe are counterproductive and undermine our collective efforts in northern Syria to defeat ISIL [DAESH]. And I've talked about this before: We believe the YPG is an effective group fighting DAESH or ISIL on the ground."

Regarding the YPG's efforts, Toner said, "They've taken additional territory outside of Afrin; they've attacked areas close to Azaz, including the Mannagh Air Base," adding that the U.S. did not "support" YPG moves near Azaz. Stressing that the situation in northern Syria is "very complex, very volatile", Toner said, "The continued regime offensive in and around Aleppo, backed by Russian airstrikes, with a variety of different groups of competing interest fighting on the ground – we don't need to add to that mix," he said.

Toner added that Washington sees no signs that Turkey is preparing for a ground invasion of northern Syria, responding to Russian allegations.

Turkey has responded to attacks from the YPG-held areas around Azaz for almost a week, following the rules of engagement, in response to activities from the terrorist group that endanger Turkey's national security.

Toner's statements on Friday regarding cooperation between Washington and the YPG raised eyebrows in Ankara, causing the latter to reiterate that they see no difference between the PKK and the YPG.

Toner avoided answering a question about a portrait of imprisoned terrorist PKK leader Öcalan hanging in the PYD's newly opened office in Moscow, indicating that he has "not seen reports" regarding the newly opened representative office, and Toner reiterated that while the U.S. sees the PKK as a terrorist organization, it does not feel the same about the PYD and the YPG who fight against DAESH in Syria.

A map on the wall of the PYD representative office in Moscow that indicates a Kurdish area in a region that includes Turkey's eastern and southeastern provinces has caused concern in Ankara. Another map with a Kurdish region called the "Kurdistan Rojava Democratic Autonomous Government" also includes areas in northern Syria currently held by opponents of the Assad regime or DAESH.

Prime Minister Ahmet Davutoğlu said last week that discriminating between terrorist organizations is as dangerous as terror and that such statements show obliviousness to reality in the Middle East, adding that Turkey is right to demand Washington clarify its stance on the PYD.

On Tuesday, U.S. ambassador to Ankara John Bass was summoned to the Foreign Ministry following remarks by U.S. State Department spokesman John Kirby that the U.S. does "not consider the PYD and the YPG as terrorists."