"This issue is like the 'tale of the scorpion and the frog.' That scorpion will definitely sting them someday due to its character," he told a gathering with village leaders at the presidential palace Wednesday, referring to the animal fable The Scorpion and the Frog, of which the morale is that one’s vicious nature never changes.

His remarks follow the recent dispute between NATO allies Ankara and Washington over the latter's objection to describe the PYD as a terrorist entity but "a reliable partner". The U.S. has also provided support for the People's Protection Units (YPG), the military wing of the PYD, in the fight against Daesh.

Turkey, a NATO ally of the U.S., calls the PYD a terrorist entity as it does the PKK.

U.S. ambassador in Ankara John Bass was summoned to the Turkish Foreign Ministry late Tuesday to express Turkey's concerns over State Department spokesman John Kirby's remarks saying: "We don't, as you know, recognize the PYD as a terrorist organization."

"Nothing has changed about our policy on that," repeated Kirby during Tuesday's press briefing while acknowledging Ankara's concerns about the group and describing Turkey as a key ally in the international anti-Daesh efforts.

The Turkish government had also recently announced its opposition to seeing the PYD participate in the Geneva peace talks on Syria.

"I told you many times. Are you with us or with this terrorist organization PYD, and YPG? What kind of an alliance is that? It is hard to understand. Although we told them a hundred times, they remain silent in our presence but say they do not recognize these groups [as terrorist] behind our back," said Erdogan.

Erdogan also lashed out at the UN's call on Turkey and EU states to take in the tens of thousands of civilians trying to escape the intensified Russian-backed air offensive on Aleppo in northern Syria.

"Then what do you [the UN] serve for? If it is that easy, I am asking you: We have accepted 3 million people from Iraq and Syria until now, but what did you accept?" he said.

"We are asking Turkey to open its border to all civilians from Syria who are fleeing danger, seeking international protection as they have done since the start of this crisis,” had said William Spindler, spokesman for the UN’s refugee agency, on Tuesday.

Erdogan stressed that the conflict in Syria had morphed into a "deportation and genocide".

"It is a case in point that those who regard the refugees as boogie men remain blind and deaf towards the Assad regime -- the real cause of this issue," added Erdogan.

Currently, Turkey hosts 2.7 million Syrian and 170,000 Iraqi refugees in both refugee camps built along its southern borders and in different cities across the country -- the world’s largest refugee population.

So far, Ankara has spent $9 billion on the refugees, while the UNHCR has only granted $455 million, according to Erdogan.

The number of refugees staying in camps stands at 280,000.

Anadolu Agency