US President Donald Trump has threatened Turkey with economic devastation if it attacks a US-allied Kurdish militia in Syria, drawing a sharp rebuke from Ankara and reviving fears of another downturn in ties between the NATO allies.

Relations between the US and Turkey have long been strained by Washington’s support for the Kurdish YPG, which Turkey views as an extension of the outlawed Kurdistan Workers Party (PKK) that is waging a decades-long insurgency in Turkey.

Mr Trump said on Sunday the US was starting the military pullout from Syria that he announced in December but that it would continue to hit Islamic State fighters there.

Speaking in Riyadh on Monday, Secretary of State Mike Pompeo said he did not think the threat would change plans to withdraw troops from Syria.

“The administration has been very consistent with respect to our requirement that the Turks not go after the Kurds in ways that are inappropriate.

“If they are terrorists, we’re all about taking down extremists wherever we find them. I think the president’s comments this morning are consistent with that.”

Asked specifically about what Mr Trump meant by devastating Turkey’s economy, Mr Pompeo replied: “We apply sanctions in many places around the world. I assume he’s speaking about those kinds of things but you would have to ask him.”

Mr Trump’s tweet drew a sharp response from Ankara and the Turkish lira lost some 0.84 per cent of its value against the dollar on Monday following the US president’s threat.

President Recep Tayyip Erdogan’s spokesman, Ibrahim Kalin, responded to Mr Trump on Twitter by saying that Turkey “fights against terrorists, not Kurds” as a people.

Mr Kalin said Mr Trump should respect Washington’s alliance with Ankara.

“It is a fatal mistake to equate Syrian Kurds with the PKK, which is on the US terrorists list, and its Syria branch PYD/YPG,” spokesman Ibrahim Kalin wrote on Twitter.

“Terrorists can’t be your partners & allies. Turkey expects the US to honour our strategic partnership and doesn’t want it to be shadowed by terrorist propaganda,” he said on Monday.

Turkish Foreign Minister Mevlut Cavusoglu also rebuked Mr Trump, saying that strategic partners do not speak to each other through social media and stressing that Turkey is “not afraid of any threat. You cannot achieve anything with economic threats.”

“We would do whatever is necessary to eliminate threat to our security,” Mr Cavusoglu added.

Mr Trump gave no details about the safe zone proposal, but Mr Pompeo said Washington wanted to provide security for those who have fought against IS and to prevent any attack on Turkey from Syria.

“If we can get the space and the security arrangements right it would be a good thing for everyone in the region,” Mr Pompeo said.

“Nothing can be achieved by threatening Turkey economically, said Mr Cavusoglu. “We need to look at how we can co-ordinate together and how we can solve this,” he said in a news conference.

The Kurdish YPG has been a US ally in the fight against the jihadists and it controls swathes of northern Syria. Mr Erdogan has vowed to crush it in the wake of Mr Trump’s decision to pull US troops out of the region.