The U.S. is “very sensitive” to Turkey’s concerns regarding the YPG, America’s top diplomat said Thursday.

John Kerry told lawmakers the U.S. has been talking “considerably” with Turkey regarding the dispute the two countries have about the group in Syria.

The YPG is the armed wing of the PKK’s Syrian affiliate PYD.

Turkey considers all three terrorist groups, but the U.S. names only PKK as a terrorist entity and says the YPG a “reliable partner” fighting Daesh in northern Syria.

“We need to respect Turkey’s concerns, and we will, we have, we believe,” Kerry said.