Turkey’s prime minister has warned his country “will fight” the United States if it stands in the way of its anti-Kurdish operations, shortly before U.S. Secretary of State Rex Tillerson is due to meet with the country’s president.

Binali Yıldırım, who serves as prime minister under President Recep Tayyip Erdoğan, told Deutsche Welle that the U.S. is violating its NATO obligations by fighting alongside the “terrorists” of the Kurdish People’s Protection Units (YPG) against the Islamic State.

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

The warning follows Erdoğan threatening that U.S. forces would receive an “Ottoman slap” if they came into conflict with the Turkish forces which have invaded Syria — a reference to the Turk-led Ottoman Empire which once conquered much of the Middle East and Europe, including Cyprus, Greece, Serbia, and Hungary.

Tuesday: Erdogan warns US about “Ottoman slap” Wednesday: pic.twitter.com/ccsbN8dcNP — Piotr Zalewski (@p_zalewski) February 14, 2018

“It is clear that those who say ‘we will respond aggressively if you hit us’ have never experienced an Ottoman slap,” Erdoğan had said, after Lt. Gen. Paul Funk had warned, “You hit us, we will respond aggressively. We will defend ourselves,” while inspecting U.S. troops in Manbij, just yards away from Turkish-backed forces.

“We will destroy every terrorist we have seen, starting with the ones standing by [the Americans’] side,” added the Turkish leader.

“Then they will understand that it is better for them to not to stand alongside the terrorists.”

US rubbishes Erdogan's 'Ottoman slap' threat as 'funny' https://t.co/btEpgCb60a — Rachel Middleton (@NewswithRachel) February 15, 2018

The war of words comes during a period of heightened Turkish aggression in Europe, with a Turkish ship ramming a Greek patrol boat in the Aegean Sea in what retired Greek admiral Grigoris Demestichas as “an intentional act of aggression … part of a design to lead to a heated episode”.

Turkish warships are also blocking an Italian drilling rig from reaching its drill site in Cypriot waters, claiming they are protecting the interests of settlers in the north of the island, which was illegally occupied by Turkey following its invasion of the Greek-speaking island in the 1970s.

The Islamist Justice and Development Party (AKP) which rules in Turkey appears to be spoiling for a showdown with the West, with Erdoğan adviser Yiğit Bulut allegedly suggesting that the U.S. is trying to encourage Greece to take on Turkey — but warning that this would be akin to “a fly picking a fight with a giant”.

Follow Jack Montgomery on Twitter: @JackBMontgomery