Turkish President Recep Tayyip Erdogan told US Defence Secretary James Mattis that Ankara is deeply concerned about US support for the Syrian Kurdish People’s Protection Units (YPG) militia, local media reported.

Mattis was in Ankara on August 23 for talks with Turkish leaders. He met with Erdogan and Defence Minister Nurettin Canikli

Turkish leaders expressed unease over increasing armed support from the US to the YPG, while Mattis sought to assuage Ankara’s security concerns, a Turkish official told Hurriyet Daily News.

The US promised Turkey to provide the serial number and delivery addresses of all arms sent to the YPG, so Turkey could monitor the process, presidential sources told the newspaper.

Ankara sees the YPG as a terrorist organisation because of its link to the Kurdistan Workers’ Party (PKK), which has been conducting an insurgency against the Turkish state since 1984.

Mattis expressed to Erdogan the US’ commitment to its bilateral relationship with Turkey and addressed Turkey’s legitimate security concerns, Pentagon Chief Spokesperson Dana White said in a statement.

Erdogan and Mattis expressed a shared interest for the two countries to create conditions for a more stable and secure region, according to the statement.

Minister Canikli and Mattis discussed the need for ongoing open and honest dialogue, and the importance of territorial integrity of Syria and Iraq, White added.

“Mattis’ visit to Ankara, which came right after his visit to Baghdad and Arbil, seems to have decreased the tension between Turkey and the US a little, if not completely,” political commentator Murat Yetkin wrote in an August 24 article for Hurriyet Daily News.

On a related note, Turkish Foreign Minister Mevlut Cavusoglu highlighted Ankara’s concerns about the Iraqi Kurdistan Regional Government‘s (KRG) plan to hold an independence referendum next month. Cavusoglu said he discussed the issue with Iraqi Kurdish leader Massoud Barzani and his delegation during a “sincere” meeting in Erbil on August 23, Reuters reported.

Turkey did not impose any demands over the vote, but urged dialogue between Erbil and Baghdad, he reportedly said.

Earlier on August 23, Cavusoglu also held talks with his Iraqi counterpart Ibrahim al-Jaafari in Baghdad. “Our expectation from Erbil is clear: that is the cancellation of the referendum as the interests and future of the Kurds lies in a united Iraq,” Cavusoglu said during a joint press conference with his Iraqi counterpart in Baghdad.