WASHINGTON - Turkey and the US were on a collision course Tuesday as President Recep Tayyip Erdogan threatened to "eliminate" a Kurdish militia in northern Syria that is part of a group allied to Washington.
US Defence Secretary Mark Esper said on Tuesday any Turkish operation into northern Syria would be "unacceptable" and the United States would prevent unilateral incursions, as tensions between Washington and Ankara simmer.
On Sunday Erdogan said Turkey, which already has a foothold in northwest Syria, will carry out a military operation in a Kurdish-controlled area east of the Euphrates in northern Syria. He said Russia and the United States have been informed of the planned operation, but did not give a date for when the offensive would begin.
Erdogan has repeatedly warned that Turkey is preparing an offensive against the Kurdish YPG militia, which the US has supported as part of the main fighting force against the Islamic State group, the Syrian Democratic Forces (SDF).
"Turkey has the right to eliminate all threats against its national security," he said in a televised speech in Ankara.
"God willing, we will carry the process started with (previous offensives into Syria) to the next stage very soon."
"Clearly we believe any unilateral action by them (Turkey) would be unacceptable," Esper told reporters traveling with him to Japan.
"What we're going to do is prevent unilateral incursions that would upset, again, these mutual interests... the United States, Turkey and the SDF share with regard to northern Syria," Esper said.
With US backing the SDF, including the YPG, have taken control over the last four years of much of northeastern Syria from Islamic State militants. Ankara sees the YPG as a terrorist organisation.
Esper said the United States did not have any "ambition" to abandon the SDF, but stopped short of guaranteeing that the United States would protect them in case of a Turkish operation.
The current US administration has previously stated, however, that it will be unable to intervene to protect its Kurdish allies in Syria and their territory in the event of an invasion.
A team from the Pentagon was in Turkey to speak with Turkish officials about the issue and Esper said he was hopeful that an agreement could be reached with Ankara.
Washington has put forward last-ditch alternative plans to stave off the Turkish military campaign that includes measure to assure Turkey's security, but it is as yet unclear whether Turkey will accept.
Esper suggested that a Turkish operation into northern Syria could affect the SDF's focus on ensuring Islamic State did not retake the territory it once held in Syria and the ability of the US-backed forces to hold the thousands of alleged Islamic State fighters in detention.
SDF officials have said they cannot defend the makeshift prisons that are holding IS captives and fight off a Turkish incursion at the same time, warning that they would most likely lose the territory they hold as well.
Aldar Khalil, a top Kurdish political official in northeast Syria, told correspondents from AFP news agency on Monday that "Erdogan is serious and will embark on an attack at the first opportunity".
"If Turkey is not deterred and a consensus is not reached for an international decision to prevent it, it will definitely be on the offensive."
Khalil said the Kurds were "flexible" on the peace talks, and had offered a five-kilometre (three-mile) buffer zone inside Syria's northeastern border with Turkey that would be cleared of YPG fighters, but this had been rejected by Turkey, which wants to push the YPG much further back from the border.
Reports suggest Turkey is insisting that the buffer zone is closer to 20 kilometres deep, and that Ankara's forces should control the area - proposals that the US has not accepted.
Ankara has pointed the finger of blame for the current situation at the US, accusing Washington of stalling progress on setting up the safe zone.
But Washington could stop any "attack with a single word... it seems they don't want to pressure Turkey more than needed," Khalil said.
The Turkish-led campaign, which has for months been delayed due to resistance from Washington, would aim to evict YPG forces from a string of border towns in Raqqa and Hasaka provinces.
Turkey sees the YPG as an offshoot of the Kurdish PKK, which has fought a bloody separatist insurgency inside Turkey for the past 35 years.
"Turkey expects steps from the US befitting of a NATO ally and strategic partner," Erdogan said on Tuesday.
"Drying up the terrorist swamp in northern Syria is our top priority."
If Turkey does go ahead with an invasion, it would mark the third Turkish incursion into Syria in as many years. Turkey has twice carried out unilateral offensives into northern Syria against the Islamic State group and YPG, in 2016 and 2018 respectively.
Turkish media outlets have often shown images in recent weeks of military convoys heading for the border area, carrying equipment and fighting units.
Ties between the two NATO allies have been strained over a host of issues, including the United States' removal of Turkey from the F-35 fighter jet program and potential sanctions against Turkey after Ankara bought and took delivery of Russian S-400 missile defences that Washington sees as a threat.