Turkish President Recep Tayyip Erdogan reacted in anger to a proposed US-trained force that could see Kurdish militiamen stationed on the Syrian side of its southern border and threatened to "drown" the initiative before it was born.
The US-led coalition confirmed yesterday that it was training recruits for a planned 30,000-strong force that will maintain security along Syria's borders with Turkey and Iraq, as well as along the Euphrates River valley.
But its manpower will be drawn from the Kurdish-dominated Syrian Democratic Forces, Washington's favoured proxy in the fight against Isis and a major source of contention with Ankara, which views Syria's Kurdish militants as an extension of a Kurdish group in Turkey that has battled the central government for decades.
Speaking today at the opening of an Ankara factory, Erdogan said it was his Government's duty "to drown this terrorist force before it is born".
"If we are strategic partners then you must carry this out with us," he said, in comments carried by the state-run Anadolu Agency.
The US-led coalition provided significant military and logistical support to the SDF as it beat back Isis (Islamic State) militants across Syria. With those largely defeated, the White House announced in November that it was preparing to halt its supply of weapons to the SDF, a mainly Kurdish force which also comprises Arab fighters.
The US-led coalition's announcement that it will now be training a border force comprising SDF fighters and recruits signals a fresh phase in Washington's commitment to Syria's Kurdish militants as it looks for ways to stabilise the territories they have recaptured.
"The US military, whether the commander and chief was [Barack] Obama or now [Donald] Trump, wants to accomplish this job with as light a US troop presence as possible," said Nicholas Heras, a fellow at the Washington-based Centre for a New American Security.
"The Trump team views Syria as irresistibly fragmented, as a fact and the result of the nature of the Syrian civil war, and President Trump is now responsible for the US zone of influence," he said.
In comments to the Reuters news agency, the coalition said the recruits would operate under SDF command and that around 230 individuals were undergoing training in its inaugural class.
Syria's Kurdish militants have emerged as one of the main winners of Syria's six-year war, capturing swaths of land in the country's north in which they are now trying to entrench their autonomy.
As a result, Turkey has shifted its focus in Syria from supporting rebel groups seeking to overthrow President Bashar al-Assad to preventing Kurdish militants from controlling more territory along its border.
Turkey has indicated in recent days that it is considering a military offensive in the Kurdish enclave of Afrin in northwest Syria. Erdogan said today that Turkish Army units had fired dozens of shells toward Kurdish positions in and around Afrin the previous day.
"We are already shooting with howitzers, and we will continue to shoot. Are we going to retreat into our shell and wait for you to hit us?" he said.