Ankara: Turkey’s foreign ministry summoned the US ambassador on Tuesday after a senior American official angered Ankara by saying that Washington did not consider the main Syrian Kurdish party to be a terrorist organisation.

The Hurriyet newspaper reported that the Turkish government, which views the Democratic Union Party (PYD) as a terrorist group, expressed its “unease” to US ambassador John Bass over the remarks by State Department spokesman John Kirby.

Kirby had told his daily press briefing in Washington on Monday: “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.”

Ankara considers the PYD and its military wing, the Kurdish People’s Protection Units (YPG), to be affiliates of the outlawed Kurdistan Workers Party (PKK), which has waged an armed insurgency in Turkey.

Kirby confirmed Tuesday that Bass had met with senior Turkish officials but declined to give further details.

He defended his earlier comments, saying “nothing has changed” on US policy.

“However, we do consider the PKK a foreign terrorist organisation and continue to be very firm about our desire to see their terrorist attacks on Turkish citizens cease,” he said.

The international coalition fighting Daesh has worked closely with the YPG since launching strikes in Syria in September 2014, expanding a campaign that began in Iraq a month earlier.

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 for several months.

Turkey fears the creation of an autonomous Kurdish region in Syria — similar to the Kurdish region in northern Iraq — would spur the separatist ambitions of Turkey’s own Kurds.

Turkish President Recep Tayyip Erdogan last week expressed anger over a US high-level delegation’s meeting with members of the powerful YPG, which is in control of the flashpoint Syrian town of Kobani.

“Do you accept the PKK as a terrorist organisation? Then why don’t you list the PYD and the YPG as a terrorist organisations, too?” Erdogan asked.

“How can we trust (you)?” he added.

“Is it me who is your partner or the terrorists in Kobani?”

Kirby had on Monday defended US support for Kurdish fighters in Syria, saying they had been “some of the most successful in going after Daesh”.

“We have provided a measure of support, mostly through the air, and that support will continue,” Kirby added.

But he said the United States was open to discussing Ankara’s concerns. “They are a friend. They are a partner,” he told reporters.

Kurdish forces backed by coalition air strikes ousted Daesh fighters from Kobani after a months-long struggle in January last year.

The Turkish government is meanwhile seeking to cripple the PKK in a relentless and controversial military campaign, while the group has killed dozens of members of the Turkish security forces in attacks since a truce collapsed in July.

The PKK launched a formal insurgency against the Turkish state in 1984, initially fighting for Kurdish independence although it now presses more for greater autonomy and rights for the country’s largest ethnic minority.

The conflict has left tens of thousands dead.

The PKK is blacklisted as a terrorist organisation by Turkey and much of the international community, including the United States.