The United States is becoming more careful in its ties with YPG militants and Ankara has seen some changes in attitude from Washington about the relationship, Turkey's presidential spokesman said on Friday.
"I see some change in the US position. I think they are being more careful," Ibrahim Kalin told reporters in Ankara.
"They have also raised concerns about the YPG's moves and connections with the Russian and the Assad regime," he said.
YPG is the militant wing of the PYD which Turkey considers as the Syrian extension of the PKK and a terrorist group though the US administration regards the group as an ally in the fight against DAESH. This has recently led to growing tension between Ankara and Washington over policy in northern Syria.
Turkey has long been confronted with armed attacks in its eastern and southeastern regions by the PKK which is listed as a terrorist organisation by Turkey, the US, NATO, and the EU while more than 300 security officers along with several civilians dying in PKK terror attacks since July 2015.
Meanwhile, US Secretary of State John Kerry said on Thursday that the US is "very sensitive" to Turkey's concerns regarding the YPG.
John Kerry told lawmakers that the US has been talking "considerably" with Turkey regarding the dispute between the two countries regarding the group in Syria.
"We need to respect Turkey's concerns, and we will, we have, we believe," Kerry said.
"We are talking with the Turks right now about how to proceed in ways that do not cross important lines for them and that respect the sensitivities of the region and I'm confident we will be able to do that," he also said.
YPG forces have exploited recent gains by forces loyal to regime leader Bashar al-Assad, backed by Russian air strikes, and seized additional territory near Turkey's border.
The YPG is currently seizing additional territory outside of Afrin, including areas close to Azaz and the Minnigh Air Base in northern Syria, areas close to the Turkish border.
Washington supports the YPG in the fight against DAESH in Syria. However, it has called on the YPG to stop seeking additional territory.
Kalin also said on Friday that Ankara is concerned with the establishment of an autonomous enclave by PKK-affiliated groups, namely YPG and PYD, near its Syrian border.
“Our problem is not with Syrian Kurds, it is with YPG. Our problem has been concerned with the creation of a state under the guidance of the PKK,” he said.