US defense officials said Thursday that USA warplanes had struck a convoy of pro-government militia forces because it was approaching a base where USA and British special operations troops trained Syrian rebels to fight the Islamic State extremist group.
The presence of regime troops so close to the deconfliction zone in At Tanif "posed a threat to US partner forces", say command officials.
Coalition forces even reached out to Russian counterparts, via the standing deconfliction channel between the two militaries, in order to halt the Iranian force advancing into the zone, command officials say.
Coalition officials initially tried to stem the advance of the Iranian convoy with a series of warning shots and US aircraft carrying out a low flyover above the convoy in a show of force.
The area around al-Tanf has been a source of tensions as both Syrian regime forces and US -backed rebels advance there trying to rout Daesh terrorist group from the region.
"On Thursday at 16.30, the so-called worldwide coalition attacked one of the Syrian Arab Army's positions on the Al-Tanf road in the Syrian Badia region, producing a number of martyrs and causing material damage", a military source told Syrian state media. Russian Federation and the coalition agree on these zones to avoid inadvertently striking each other's forces.
United States of America military officials have not yet determined if Syrian army forces were targeted in the strike or if they were militias aligned with the government of Syrian President Bashar Assad.
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The army described the attack as a "flagrant aggression", and added that it exposes the "false allegations of the coalition about fighting terrorism".
Reuters reported Russian Deputy Foreign Minister Gennady Gatilov as saying the USA strike had violated Syria's sovereignty and would not help efforts to find a political solution to the conflict.
"Targeting our presence in Syria is targeting us in Iraq, too, and we will strike the enemy and its supporters everywhere", the statement said. On the ground, the US presence in Syria is also becoming more visible, as American troops back Kurdish-led forces fighting the Islamic State.
Russia's deputy foreign minister Gennady Gatilov said the destruction of the convoy was a "breach of Syrian sovereignty" and an attack against Syrian armed forces was "completely unacceptable". "But it looks like the Russians tried to dissuade them", Mattis said. An array of regular and irregular forces are battling alongside the government against rebels, including Russian and Iranian soldiers and militants from Iraq and Lebanon's Hezbollah group.
Coalition forces have operated in the al Tanf area for many months training and advising vetted partner forces who are fighting ISIS.
Syria's conflict erupted in March 2011 with widespread demonstrations against Assad, but has since evolved into a bloody war that has drawn in world powers on all sides.
A western diplomat in Geneva said the UN's initiative on constitutional meetings was an effort to "get people into substance".