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Following its forceful defense of its toehold in south Syria, around the Al-Tanf rebel base near the Jordanian border, the United States is bolstering and expanding this position by reportedly incorporating another base with its anti-Islamic State (IS) Syrian rebel allies.

On US-led coalition air power intentionally bombed pro-Syrian regime forces who approached Al-Tanf, which they described as a "well-established deconfliction zone". Also on June 8, the coalition shot down an Iranian-made drone which attempted to fire at their positions.

These attacks were the first of their kind. US Secretary of Defense James Mattis characterised them as defensive. US Central Command (CENTCOM) has also sought to emphasise that the coalition in Syria's main aim is the defeat of IS.

"The coalition does not seek to fight Syrian regime, Russian or pro-regime forces partnered with them," . "The demonstrated hostile intent and action of pro-regime forces near coalition and partner forces in southern Syria, however, continue to concern us, and the coalition will take appropriate measures to protect them."

At Al-Tanf, the US and its British coalition have been training a few hundred Jaysh Maghawir al-Thawra - previously known as the New Syrian Army (NSyA) - anti-IS fighters. Their stated aim is to remove IS from swaths of the Deir Az-zour province.

Syrian regime forces are also advancing in the same area, likely aiming to reestablish their presence in eastern Syria, where they've only managed to maintain an army garrison in the provincial capital of Deir Az-zour against IS for the last three years. This garrison is increasingly under siege, and may even be overrun in the near future if Damascus is unable to reinforce it.

Syrian regime forces are also advancing in the same area, likely aiming to reestablish their presence in eastern Syria

According to one official, the exclusion zone enforced by the coalition around Al-Tanf is . Al-Thawra's spokesman, Abu al-Atheer, that this zone is being expanded to incorporate a second base in Zakf, approximately 60-70km northeast of Al-Tanf.

This could potentially increase the likelihood of future clashes and escalation between the coalition and regime forces in that region. 

Also this month High Mobility Artillery Rocket Systems (HIMARS) into this exclusion zone, enabling them to bombard targets from 300km away. The US previously deployed the same systems to an abandoned airbase south of Mosul, enabling them to strike any part of the city, and in northern Syria, to support the Syrian Democratic Forces (SDF) Arab-Kurdish coalition fighting IS in Raqqa.

HIMARs in south Syria could lend fire support to the Thawra fighters if air power is unavailable. In July 2016 US fighter jets were supporting Thawra fighter in an offensive against IS in the town of Bukamal in Deir Az-zour province, more than 300km from Al-Tanf, when into the desert in neighbouring Iraq. IS subsequently beat back the Thawra offensive.

Damascus is irked by the coalition presence in Al-Tanf, which reportedly includes along with ground forces from five other coalition countries and have even threatened Jordan, which is the main host country for this training and deployments. 

"We are not seeking a confrontation with Jordan, but if Jordanian forces enter our territories without coordination with Damascus, we will consider them adversaries," Syria's Foreign Minister Walid Moallem on May 8.

The coalition has repeatedly emphasised the fact the forces they are closely supporting are solely being used against IS. However, it refuses to coordinate operations in Syria with Damascus, and it's not yet clear if the territory they seize from IS will be immediately ceded back to regime control.

When Turkey cleared IS from their northwest border region in the now concluded Euphrates Shield operation (August 24, 2016 – March 29, 2017) using a proxy Syrian militia, it did not withdraw but held onto these territories and continues to use them as a buffer zone.

Ad-hoc coordination and deconfliction measures the US has long had in place with the Russian military in Syria, could help avoid any future clashes or potential escalation.

The US coalition refuses to coordinate operations in Syria with Damascus, and it's not yet clear if the territory they seize from IS will be immediately ceded back to regime control

The US even recently with calming the situation around Al-Tanf from escalating.

Pentagon spokesman Jeff Davis said that: "Russia has been very helpful and I think the calm that we see today is largely due to their efforts."

In addition, last month US Major-General Joseph Dunford that they have already "talked about that [Deir Az-zour] as a specific area that requires" avoiding any clashes with the Russians.

"My sense is that the Russians are as enthusiastic as we are to de-conflict operations and ensure that we continue to take the campaign to ISIS and ensure the safety of our personnel."

Nevertheless, Russian Foreign Minister Sergei Lavrov  US Secretary of State Rex Tillerson to halt further attacks against these regime forces as they continue operations in the southern region.

"Lavrov expressed his categorical disagreement with the US strikes on pro-government forces and called on him to take concrete measures to prevent similar incidents in future," read a Russian Foreign Ministry statement on the phone call.

Both sides emphasised the need for coordination. They could feasibly work together to delegate separate areas of responsibility for regime forces and Thawra to seize from IS to avoid further clashes and the risk of escalation into a full-blown war in that increasingly volatile border region. 


Paul Iddon is a freelance journalist based in Erbil, Iraqi Kurdistan, who writes about Middle East affairs.

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