Secretary of State Rex Tillerson begins a pivotal visit to Turkey on Thursday evening intended to mend fences amid President Recep Tayyip Erdogan’s repeated threats to attack U.S. soldiers in Syria.

Erdogan has insisted that his troops will enter Manbij, a region of northern Syria populated in part by U.S. troops. Turkey objects to Washington’s support of the Syrian Kurdish People’s Protection Units (YPG/YPJ), a militia that was instrumental in the defeat of the Islamic State in its “capital,” Raqqa.

In remarks Tuesday, Erdogan threatened the United States with an “Ottoman slap,” a medieval martial arts technique. State Department spokesperson Heather Nauert refused to get “riled up” about the comment during her regular press briefing that day.

Tillerson will meet Erdogan personally this week in Ankara and also hold talks with Foreign Minister Mevlut Cavusoglu, according to Turkey’s state news agency Anadolu. Tillerson is currently on a Middle East tour that also includes Jordan and Lebanon.

In Lebanon Thursday, Tillerson affirmed in response to reporters’ questions during a press conference with Prime Minister Saad Hariri that “Turkey is an important NATO ally of ours, they’re still an important partner of ours in the fight to defeat ISIS.”

Tillerson praised Ankara as having “performed admirably” and “been supportive” of the United States.

“There are so many aspects of the Turkey-U.S. relationship which are very important and very positive, and we intend to build on the areas that we do share common interests, common concerns,” Tillerson continued. “I would tell you our endpoint objectives are completely aligned; there’s no gap between them.”

Tillerson also claimed that the United States has “never given arms to the YPG.”

In May, President Donald Trump approved weapons shipments for the Syrian Defense Forces (SDF), an umbrella group primarily composed of members of the YPG. Prior to that announcement, an SDF spokesman said the United States had begun to provide “signs of full support” to the Kurds under Trump.

Speaking to reporters from Brussels, Secretary of Defense Jim Mattis appeared to echo Tillerson’s optimism on Turkey. “I believe we are finding common ground and there are areas of uncommon ground, where sometimes war just gives you bad alternatives to choose from,” he said. “We continue to collaborate on ways to ensure their legitimate concerns are addressed.”

His Turkish counterpart, Defence Minister Nurettin Canikli, seemed significantly less positive about the meeting. Canikli claimed that Mattis had insisted Turkey accept that the YPG and the Kurdistan Workers’ Party (PKK), a Marxist terrorist group active in Turkey, were separate entities. The United States has designated the PKK a terrorist organization while supporting the YPG as a separate, Syrian entity.

“I told him that this is not a realistic approach. The YPG is part of the PKK and it’s impossible that they would fight each other,” Canikli said of Mattis’s proposal.

It is unclear how Tillerson’s efforts with Erdogan may conclude in a different result than Mattis’s with Canikli. Deputy Premier Bekir Bozdag preempted Tillerson’s arrival Thursday with similar comments, insisting that Tillerson not attempt to convince the Turks of anything.

“The U.S. should stop trying to convince us to see another reality. We do not need to be convinced on this issue. Because the reality is clear,” Bozdag insisted, according to Anadolu.

Prime Minister Binali Yıldırım, meanwhile, openly stated that the Turkish military will shoot U.S. soldiers if Erdogan does not get his way.

“We have a problem with the YPG, but if the United States begins warring against us by the side of the YPG, we will fight them as well,” he warned.

Pro-Erdogan media has also increased its belligerence towards Washington in anticipation of Tillerson’s visit. Anadolu published a report, citing Iranian government sources, that the United States had transported Islamic State terrorists to Afghanistan. Yeni Safak, an Islamist newspaper, has declared Syria a “shattering defeat” for the West generally.

Sabah, yet another pro-government publication, printed an open letter to Tillerson warning him to “carefully weigh what you will say to Turkish officials” and proclaiming that “Turkey has neither the patience to wait any longer nor the tolerance to listen to any more empty statements.”

“If you behave, we will be a great friend,” Sabah demands.

Turkey launched Operation Olive Branch in Afrin, northwest Syria, last month, a project to invade and colonize areas of Syria controlled by the YPG. There are no U.S. troops in Afrin and the United States has done nothing in support of YPG fighters there. Washington has expressed concern, however, that Erdogan has threatened to move into Manbij, which does have a U.S. presence.

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