Turkish-backed forces came “very close” to U.S. troops in Syria just west of a coalition base in the northern Syrian town of Ain Issa Tuesday — so close that American jets and attack helicopters were called in to disrupt the approaching forces, a U.S official tells Fox News.

The Turkish-backed fighters “violated a standing agreement with the U.S. not to get close enough to threaten U.S. troops,” the official said.

Air Force F-15 fighters and Army Apache attack helicopters arrived on the scene. The Apache hovered between the U.S. troops and the approaching forces, just feet off the ground.

TRUMP SAYS U.S. TROOPS IN SYRIA TO BE WITHDRAWN, REDEPLOYED IN REGION

The U.S. military lodged a formal complaint with the Turkish military after the incident through diplomatic channels. The American Special Operations forces were partnered with Syrian Kurdish allies during the encounter, which took place a few hours ago, the official added.

According to U.S. Army Col. Myles B. Caggins III, a spokesman for Operation Inherent Resolve, based in Baghdad: “As Turkish-backed militias advanced towards the Lafarge Cement Factory, between Kobanî and Ain Issa, on Tuesday, Oct. 15, the SDF set fire to, then vacated, its facilities and equipment. The location had been the headquarters of the de facto Defeat-ISIS coalition in Syria. No U.S. forces or equipment were ever in jeopardy and remain within separate, secure facilities. Our priority is protecting the remaining Coalition forces at the LCF as multiple forces converge in northeast Syria. Coalition forces are executing a deliberate withdrawal from northeast Syria.”

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The Turkish military considers the Kurdish-led Syrian Democratic Forces, the main U.S. ally against ISIS, as terrorists linked to a decades-old insurgency in Turkey, which has killed tens of thousands of people since the mid-80s.

The United Nations has said that as many as 160,000 people, including 70,000 children, have been displaced since the fighting in northeast Syria escalated nearly a week ago.