♦ Damascus vows to drive US troops from country

♦ Russia says US does not want to maintain Syrian unity

Turkey's Tayyip Erdogan yesterday threatened to "strangle" a planned 30,000-strong US-backed force in Syria "before it's even born," as Washington's backing for Kurdish fighters drove a wedge into relations with one of its main Middle East allies.

The United States announced its support on Sunday for plans for a "border force" to defend territory held by US-backed, Kurdish-led fighters in northern Syria.

The Syrian government of President Bashar al-Assad responded yesterday by vowing to crush the new force and drive US troops from the country. Assad's ally Russia called the plans a plot to dismember Syria and place part of it under US control.

But the strongest denunciation came from Erdogan, who has presided as relations between the United States and its biggest Muslim ally within Nato have stretched to the breaking point.

"A country we call an ally is insisting on forming a terror army on our borders," Erdogan said of the United States in a speech in Ankara. "What can that terror army target but Turkey?"

"Our mission is to strangle it before it's even born."

Erdogan said Turkey had completed preparations for an operation in Kurdish-held territory in northern Syria.

The United States has led an international coalition using air strikes and special forces troops to aid fighters on the ground battling Islamic State militants in Syria since 2014. It has about 2,000 troops on the ground in Syria.

The US intervention has taken place on the periphery of a near seven-year civil war that has killed hundreds of thousands of people and driven more than 11 million from their homes.

Islamic State was effectively defeated last year, but Washington says its troops are prepared to stay to make sure the Islamist militant group cannot return, also citing the need for meaningful progress in UN-led peace talks.

For much of the war, the United States and Turkey worked together, jointly supporting forces fighting against Assad's government. But a US decision to back Kurdish fighters in northern Syria in recent years has enraged Ankara.