The Turkish government, which views the Democratic Union Party (PYD) as a terrorist group, expressed its "unease" over the remarks by Kirby during his daily press briefing in Washington yesterday, the Hurriyet newspaper reported.
"We don't, as you know, recognise the PYD as a terrorist organisation. We recognise that the Turks do, and I understand that. Even the best of friends aren't going to agree on everything," Kirby said.
For several months, the US-led coalition's support for the PYD and the YPG has been a source of friction between Washington and its NATO ally Ankara.
Turkish President Recep Tayyip Erdogan last week expressed anger over a US high-level delegation's meeting with members of the YPG, which is in control of the flashpoint Kurdish town of Kobane.
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