U.S. State Department spokeswoman Heather Nauert said Turkish President Recep Erdoğan’s threat to deliver an “Ottoman slap” to U.S. troops in Syria was funny as the reporters at her press briefing laughed when she was asked if the United States had experienced such a blow.

The United States and Turkey are at odds over U.S. support for Kurdish forces in Syria. The U.S. military has backed the mainly Kurdish People’s Protection Units (YPG) and together they have pushed Islamic State (ISIS) out of most of northern Syria to a remote area astride the border with Iraq.

Turkey sees the YPG as an arm of Kurdish rebels in Turkey and launched an operation against the group in the northwestern Syrian enclave of Afrin three weeks ago. Erdoğan has also threatened to pursue the offensive to into the area around the Syrian town of Manbij where U.S. troops are training the Kurdish forces.

U.S. Lieutenant General Paul Funk, the commander of the U.S.-led coalition against ISIS, said last week on a visit to Manbij that U.S. forces would defend themselves if attacked. “You hit us, we will respond aggressively. We will defend ourselves,” he said.

Erdoğan hit back on Tuesday. “Those who say 'if they hit us we will respond harshly' have clearly never received an Ottoman slap."

The full-bodied blow with the palm of the hand is said to have been used by Ottoman Empire forces to incapacitate their enemies when they found themselves unarmed.

“Has the U.S. experienced the Ottoman slap?" a reporter asked Nauert at her State Department briefing. Smiling, she turned her head away and took a moment to collect herself as journalists laughed.

“As funny as it was the comment that you explained to me, I’m not going to respond to every foreign leader’s comment,” she said.

Instead, she said U.S. officials had held a series of high level meetings with their Turkish counterparts, and added that in those meetings, U.S. officials had expressed their concerns, “about the escalation of violence in Syria, in particular in the Afrin area, which, by the way, we are not operating, but nonetheless, it is a concern of ours.”

U.S. officials are concerned the Turkish operation could spark to new areas of conflict in Syria and that it could draw Kurdish fighters from the front against ISIS.

U.S. Secretary of State Rex Tillerson, on a tour of the Middle East this week, called the Afrin operation a “distraction” and said, “as we all know, there are other terrorist elements operating inside of Syria, including al Qaeda - which is a threat to the United States - Nusra Front, and others. So we want to work together to maintain our focus on the essential mission of defeating ISIS."

Turkey, for its part, sees the YPG as an crucial threat to its security.

Asked whether any progress had been made with the Turkish government with regards to these issues, Nauert said, “one of the bigger ways that we are making progress is that the secretary is going there to Turkey himself. I think that shows just how serious this matter is, and how seriously regarded.”

Tillerson is expected to meet his counterparts in Ankara on Friday. Turkish officials, including Erdoğan, have been upping the ante this week to argue that the Tillerson’s visit will be make or break for the future of Turkey-U.S. relations.

Turkish media reports said Ankara municipality was considering renaming the street where the U.S. Embassy is located “Olive Branch”, after the name of the Turkish operation in Afrin.

Nauert said they could call the street “whatever they want”.

Asked about Turkish leaders’ rising anti-U.S. rhetoric, the spokeswoman was relaxed. “We’re used to that kind of rhetoric, whether it’s from the Turkish government or from other governments, and so that’s why we don’t get too riled up about that.”

“But most of the other countries that criticise you in these terms are not your allies,” a reporter interrupted.

“It doesn’t matter, doesn’t matter. We’re not going to go there. We’re taking the high road,” Nauert said.

The State Department for the first time acknowledged the detention of another U.S. Consulate employee in Turkey. Nauert said she was aware of the situation, but added she does not have any information to share at this time.

The deputy head of security at the U.S. Consulate in Istanbul was handed over to authorities by diplomatic staff on Jan. 31 and has been under house arrest with an electronic tag since, the pro-government Sabah newspaper said.

Another consulate employee, who was a liaison officer with the Turkish security authorities, Metin Topuz, was arrested last year. The U.S. government lifted all visa services in Turkey for several months in response.

Tens of thousands of people have been arrested in Turkey in an ongoing crackdown on dissent under state of emergency powers introduced after a failed coup in 2016.

A Turkish court on Monday sentenced Enis Berberoğlu, a member of parliament for the main opposition Republican People’s Party (CHP), to five years and 10 months in jail after convicting him of leaking to the press pictures of weapons being sent by the Turkish intelligence service to Syria.

The U.S. Government finds this case to be “complex”, Nauert said, but added, “we remain seriously concerned about the widespread arrest and pre-trial detention in Turkey of a range of individuals who are critical of the Turkish government. He was one who was considered to be critical of the Turkish government.”

The U.S. administration has been urging the Turkish government to respect the rule of law and ensure fundamental freedoms and rights very often in recent months. Tuesday was not different. Spokeswoman once again made firm calls on the Turkish Government to make a progress on these issues:

“We want to take this opportunity to remind the government of Turkey that freedom of expression, including freedom of speech, freedom for the media to operate – I know our Turkish reporters care very deeply about that – freedom of speech, including times when that speech can become very uncomfortable for a government or a regime – that needs to be protected, that freedom of speech. More voices, not fewer voices, are necessary in some of these challenging times. We want to urge Turkey to respect and ensure freedom of the press, fair trial guarantees, judicial independence, and other human rights and fundamental freedoms.”