President Donald Trump threatened Turkey with devastating sanctions if America's NATO ally attacked Kurds following a U.S. troop withdrawal from Syria.
"Starting the long overdue pullout from Syria while hitting the little remaining ISIS territorial caliphate hard, and from many directions," Trump said on Twitter late Sunday. "Will attack again from existing nearby base if it reforms. Will devastate Turkey economically if they hit Kurds. Create 20 mile safe zone...."
"...Likewise, do not want the Kurds to provoke Turkey," the president added in another tweet.
The White House, State Department and Pentagon did not respond to CNBC requests for comment or elaboration.
Turkish Foreign Minister Mevlut Cavusoglu responded, saying that nothing could be achieved with economic threats and that partner nations shouldn't communicate over social media, Reuters reported Monday. The minister added that Trump's Syria tweets stemmed from domestic politics.
American support for Kurdish militias in Syria has been a major thorn in relations between Washington and Ankara, as the latter views the Kurds as terrorists and a threat to their security.
The militias, known as the Kurdish People's Protection Units (YPG), are the armed wing of the Democratic Union Party (PYD), an offshoot of the designated terrorist group called the Kurdistan Workers' Party, which has carried out a decades-long insurgency against the Turkish state. They are also America's primary partners on the ground in Syria: The Pentagon has been supplying the YPG with weaponry, air support and training to battle IS since 2015, and the militias have suffered thousands of casualties fighting for the U.S.-led coalition.
Ankara has for months threatened a military offensive against the Kurds in northeastern Syria, refusing to view their presence as legitimate. Thousands of Turkish troops have taken positions along the Syrian-Turkish border amid warnings from President Recep Tayyip Erdogan of an "imminent" Turkish attack.
Following a torrent of domestic and international criticism for what many called an abandonment of its partners, Trump administration officials last week framed the withdrawal of the roughly 2,000 U.S. troops deployed in Syria as contingent on a guarantee of Turkish nonaggression and protection for the Kurds.
Turkey's politicians, including Erdogan, have flatly rejected the American efforts.
The last year was a largely fraught one between the longtime NATO allies thanks to heightened tensions over Syria policy, Turkey's purchase of Russian weapons systems alongside American ones, and Ankara's detention of American pastor Andrew Brunson. The latter diplomatic crisis prompted Trump in August to announce sanctions on Turkish officials and threaten new tariffs.
Last summer, Turkey's lira — already falling due to a gaping current account deficit, over-leveraged banks and its president's refusal to raise interest rates despite double-digit inflation — tanked further after Trump threatened to double tariffs on Turkey's steel and aluminum. By August, the currency had depreciated by some 40 percent against the dollar since the start of 2018.
The lira has since rebounded, though not to its mid-2017 levels of roughly 3.5 lira to the dollar. The currency saw major relief after Ankara agreed to release Brunson to the U.S. in October and the tariff threats were walked back.
The dollar strengthened against the lira on Monday with 5.49 liras to the greenback.
Speaking to CNBC Monday, retired Gen. James Jones, a former U.S. national security advisor and former supreme allied commander of NATO forces in Europe, said the conflicts between Washington and Ankara should not be litigated in public, but rather by careful discussion between the two governments.
"You really have to have serious meetings at both capitals with the intent of fixing what right now is somewhat fractured," he said.
— CNBC's Shirley Tay contributed to this report