Turkey had accused the United States of supporting "terrorists" after Washington declined to immediately back Ankara's claim that Kurdish militants had executed 13 Turkish nationals in Iraq.

"The Secretary expressed condolences for the deaths of Turkish hostages in northern Iraq and affirmed our view that PKK terrorists bear responsibility," State Department spokesman Ned Price said in a statement.

The Turkish anger was directed at a US State Department statement on Sunday saying Washington "deplores the death of Turkish citizens" but awaits further confirmation of Ankara's version of events.

Turkish President Recep Tayyip Erdogan branded Washington's response "a farce" and the Turkish foreign ministry summoned US Ambassador David Satterfield to express Ankara's displeasure "in the strongest possible terms."

Price said Blinken spoke by phone with Cavusoglu on Monday and "emphasized the longstanding importance of the US-Turkish bilateral relationship" and "our shared interest in countering terrorism."

He said Blinken also urged Turkey "not to retain the Russian S-400 surface-to-air missile system."