The US has rubbished the "Ottoman slap" threat issued by Turkey's President Recep Tayyip Erdogan over a possible confrontation between American and Turkish military personnel in the ongoing conflict in Syria.

The two sides are operating dangerously close to each other in the strife-torn Syrian region where the US backs the YPG Kurdish fighters, who are regarded as "terrorists" by Ankara. Following a sudden escalation of the anti-Kurdish offensive in recent weeks by Turkey, concerns have surfaced that the situation could put the US and Turkey, both Nato members, at the opposite sides of the war zone directly.

Amid the volatile atmosphere, Erdogan had warned Turkish forces will not return until they wipe out the Kurdish militants in the region and asked the US to stop funding the Kurdish fighters or face Turkey's wrath.

"We will destroy every terrorist we have seen, starting with the ones standing by their side. Then they will understand that it is better for them to not to stand alongside the terrorists," the Turkish president told the parliament.

"It is clear that those who say 'we will respond aggressively if you hit us' have never experienced an Ottoman slap," he said. "They have mistaken Turkey for the kind of place where they can come and go as they please without giving an account. They will soon see that it's not such a place."

Erdogan's remarks come in the wake of an imminent visit by the US Secretary of State Rex Tillerson, who is set to hold talks with top Turkish officials on Thursday and Friday (15, 16 February) in easing the situation and to avoid a showdown.

But, the US State Department called Erdogan's threat as "funny". The department's spokeswoman Heather Nauert said: "As funny as it was the comment that you explained to me, I'm not going to respond to every foreign leader's comment."

In January, Turkey had launched a major military offensive, codenamed "Operation Olive Branch", against Kurdish insurgents in Syria's Afrin and Manbij, the area where Washington has deployed its personnel in training capacity. The operation is still underway.

Operation Olive Branch Afrin Syria
A picture taken on February 5, 2018, on a mountain on the Syrian-Turkish border, north of Azaz SALEH ABO GHALOUN/AFP/Getty Images