The U.S. military carried out an air strike on Thursday against militia supported by the Syrian government who had moved against U.S.-backed fighters in the country's south, a U.S. official told Reuters on Thursday.
The official, who spoke on condition of anonymity, said the strikes took place near the town of At Tanf and followed warning shots by U.S. aircraft meant to disuade the fighters.
U.S. official said the strike hit a tank and a bulldozer and forces there, but it was not clear if they were Syrian army troops or other pro-government allies.
One official said the pro-regime forces had entered a so-called "de-confliction" zone without authorization and were perceived as a threat to U.S.-allied troops there. The officials said the strike was a defensive move to protect the U.S. allies. It wasn't clear if U.S. forces were there.
The officials weren't authorized to speak publicly on the matter and demanded anonymity.
A commander in the alliance fighting in support of Syrian President Bashar Assad called the airstrike a "warning raid."
"The raid only destroyed a tank. It did not aim to cause casualties or damage, but to stop an attack" and advance by Syrian government forces and allied militia, said the non-Syrian commander.
A rebel official said the airstrike destroyed a Syrian army and Iranian-backed militia convoy heading to the Tanf base in southern Syria.
The area has been a source of tensions as both government forces and U.S.-backed rebels advance there. Both the government forces and the rebels are trying to rout Islamic State militants from the area.
Muzahem al Saloum, from the Maghawir al Thwra group, told Reuters that the jets struck after rebel forces clashed with advancing Syrian and Iranian militias that were about 27 kms away from the base along the Damascus-Baghdad highway.
"We notified the coalition that we were being attacked by the Syrian army and Iranians in this point and the coalition came and destroyed the advancing convoy," Saloum said.
Said Seif, an official with the Western-backed Free Syrian Army Shahid Ahmed Abdo rebel group, said the U.S. intervention will help the rebels to hold their ground against any future incursions by the army and its Iranian backed militias.
Western intelligence sources told Reuters that U.S. and British special forces are expanding the Tanf base to oust Islamic State militants from the eastern province of Deir Zor, that straddles Iraq, from the south east of Syria.
The Damscus-Baghdad highway was a major weapons supply route for Iranian weapons into Syria until Islamic State seized territory along the Iraqi Syrian border, regional intelligence sources says.
The Syrian army had been sending reinforcements in the last few weeks to the desert region near its border with Iraq and Jordan.
They captured the remote town of Sabaa Biyar near the strategic Damascus-Baghdad highway in an attempt to prevent areas left by Islamic State hardline militants in March from falling into the hands of Western-backed moderate Free Syrian Army (FSA) rebels.
Regional intelligence sources and rebels say the ultimate goal of the Syrian army's push in the Badia was to link its forces with Iraq's Shi'ite paramilitary groups on the other side of the border.
The Shi'ite troops launched an offensive on Friday to drive the militants from the desert region near the border with Syria. . Iraqi Shi'ite militia leaders said they hoped to link up with Syrian government forces.
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