Trump threatens to 'devastate' Turkish economy if Kurds attacked

US President Donald Trump has threatened to "devastate" Turkey’s economy if President Recep Tayyip Erdogan orders attacks on Kurdish forces in Syria after a planned withdrawal of US troops.

US forces fighting Islamic State militants in Northern Syria have cooperated with the Kurdish People’s Protection Units (YPG), which leads the US-backed Syrian Democratic Forces (SDF) but is regarded as a terrorist organisation by Erdogan’s administration.

Trump’s Sunday night tweet said: "Starting the long overdue pullout from Syria while hitting the little remaining ISIS territorial caliphate hard, and from many directions. Will attack again from existing nearby base if it reforms. Will devastate Turkey economically if they hit Kurds. Create 20 mile safe zone...."

The tweet was accompanied by a warning to Kurds not to provoke Turkish forces and has sent Turkey’s lira sharply lower.

No mention was given as to how any safe zone might be enforced, though US Secretary of State Mike Pompeo is understood to be attempting to negotiate a deal while on a tour of the Middle East to reassure US allies in the region.

"The US is withdrawing from northeast Syria in a strong, deliberate and coordinated manner, and seeks to ensure that the forces that have fought alongside coalition partners in the campaign against ISIS are not mistreated," said an official from the Trump administration.

Trump’s decision to withdraw the 2,000 American troops from Syria led to the resignation of Defense Secretary James Mattis and was met with criticism from allies and adversaries.

Turkey's foreign minister, Mevlut Cavusoglu, responded to Trump's Sunday night tweets by stating that Turkey would not be deterred by US threats and criticised Trump’s use of social media to discuss strategic alliances.

Meanwhile, President Erdogan’s spokesman Ibrahim Kalin tweeted: "Mr @realDonaldTrump 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."

Turkish forces have reportedly amassed at the border with Syria in the weeks since Trump announced US withdrawal from the country, stoking fears of an attack on the YPG.