USA commanders became concerned when they saw tanks, bulldozers and other heavy equipment advance into a "de-confliction" zone without authorization near a base where US forces were located, according to the officials, who spoke about the incident after requesting anonymity because they were not authorized to discuss the matter publicly. Coalition forces even reached out to Russian counterparts, via the standing deconfliction channel between the two militaries, in order to halt the Syrian troops advancing into the zone, command officials say.
The U.S. -led coalition reportedly also tried to warn the Syrian government through a hotline established with Assad-allied forces, but that didn't work.
Strike is seen as defense and not signaling a switch in the United States strategy in Syria from fighting ISIS to fighting the Assad regime. Reuters reports that the usa fired warning shots at some point before Thursday's strike.
The airstrike appears to be the first publicly known direct confrontation between USA forces and fighters loyal to Syrian President Bashar al-Assad.
Coalition warplanes targeted a convoy of Syrian government forces and Iranian-backed militia close to the Iraq border on Thursday.
He was asked if the airstrike increases the United States role in the Syrian war. Since then it has seen massive worldwide involvement and the rise of the Islamic State of Iraq and Syria (ISIS), and has resulted in almost 500,000 casualties, over 4 million refugees, and over 7 million internally displaced people.
US-backed rebels have secured larges areas of the Badia from Islamic State in recent months, but the Syrian army and Iranian-backed militia have moved hundreds of troops with tanks to the town of Sabaa Biyar, near the strategic Damascus-Baghdad highway.
However, the Al Tanf attack raises questions about the ongoing feasibility for the US-led coalition to maintain its singular focus on the Islamic State of Iraq and the Levant (ISIL) group.
The Syrian-allied forces were threatening US troops and allied rebel forces operating near the town of Al-Tanf on Syria's border with Jordan, and were hit with air strikes after Russian intervention and warning shots failed to deter them, the Pentagon said on May 18.More news: Trump alleges 'witch hunt', denies trying to kill FBI probe
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The forces came within a 34-mile defensive zone around the at-Tanf base in southern Syria, according to the command.
Attempts to stop the convoy included a call to the Russians - who are working with the Syrian regime - then a "show of force" in the skies above the vehicles, followed by warning shots.
"Coalition forces have been operating in the At Tanf area for many months training and advising vetted partner forces engaged in the fight against ISIS".
The convoy was hit on Thursday as it neared a group of US-backed rebels and a Western special forces unit in Tanf.
As the Wall Street Journal's Yaroslav Trofimov notes, Thursday's strike is significant not because the US has once again struck Assad's forces, but because it did so in defense of Syrian rebels.
According to the media outlet, US officials explain the strikes as "force protection" for the US Special Forces based in the area.
A convoy of 20 pro-regime vehicles were headed toward An Tanf Wednesday night, searching vehicles and buildings along the way, according to a U.S. official.
The first official said the convoy was "significant" in size, but only the lead vehicles were hit.