Beirut • Turkish President Recep Tayyip Erdogan reacted in anger Monday to a proposed U.S.-trained force that could lead to Kurdish militiamen being stationed on the Syrian side of Turkey's southern border, threatening to "drown" the force before it is born.

The U.S.-led coalition confirmed Sunday that it is training recruits for a planned 30,000-strong force that will maintain security on 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 favored proxy in the fight against the Islamic State and a major source of contention with Ankara, which views Syria's Kurdish fighters as an extension of a Kurdish group in Turkey that has battled the central government for decades.

Speaking on Monday at the opening of an Ankara soda factory, Erdogan said it is his government's duty "to drown this terrorist force before it is born."

The U.S.-led coalition provided significant military and logistical support to the SDF as it beat back 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 that also includes Arab fighters.

The coalition's announcement that it will now be training a border force comprising SDF members and recruits signals a fresh phase in Washington's commitment to Syria's Kurdish fighters as it looks for ways to stabilize the territories they recaptured from the Islamic State.

"The U.S. military, whether the commander in chief was Obama or now Trump, wants to accomplish this job with as light a U.S. troop presence as possible," said Nicholas Heras, a fellow at the Washington-based Center 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 Donald Trump is now responsible for the U.S. zone of influence," he said.

In comments to the Reuters news agency, the coalition said that the recruits would operate under SDF command and that about 230 individuals are undergoing training in its inaugural class.

Syria's Kurdish fighters have emerged as one of the main winners of the country's six-year war, capturing swaths of land in the country's north.

As a result, Turkey has shifted its focus in Syria from supporting rebel groups seeking to overthrow President Bashar Assad to preventing Kurdish fighters 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 northwestern Syria. Erdogan said Monday that Turkish army units had fired dozens of shells toward Kurdish positions in and around Afrin the previous day.