Updated at 8:51 a.m.
The tensions between the two superpowers were strained once again with Sunday's downing of a regime fighter jet by USA -led coalition in Syria as Russian Federation said Monday it will treat US -led coalition planes in Syria, west of the Euphrates, as targets.
The Syrian army backed by Iranian-backed militias has also been in competition in southeastern Syria with US -backed Free Syrian Army (FSA) rebels who are also trying to recapture territory from ISIS.
Russia was so incensed by the Sunday shoot-down that it threatened USA aircraft in the western half of Syria, saying that "any aircraft, including planes and drones of the global coalition, detected in the operation areas west of the Euphrates River by the Russian air forces will be followed by Russian ground-based air defense and air defense aircraft as air targets".
The Russians, who have been providing air cover for Assad's forces since 2015, appear to want to avoid further USA targeting of Syrian warplanes or ground troops that have come under US attack in eastern Syria recently.
The Russian announcements came in response to the downing of the Syrian Air Force plane, which was the first time for the United States after it began fighting the IS in Syria, leading a coalition of worldwide forces, in 2014.
The US statement said that coalition aircraft stopped a "pro-regime advance" toward an "SDF-controlled town". While the US has said since it began recruiting, training and advising what it calls moderate Syrian opposition forces to fight IS that it would protect them from potential Syrian government retribution, this was the first time it resorted to engaging in air-to-air combat to make good on that promise.
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Government forces and their allies are working in eastern areas, and have clashed with the United States and their partners as they carry out operations.
In a statement, the defence ministry said that starting today it will track all jets and drones from the coalition in the area.
The US military statement says it acted in "collective self-defense" of its partner forces and that the US does not seek a fight with the Syrian government or its Russian supporters.
Earlier, Syrian forces attacked Coalition fighters in Ja'Din, wounding a number of fighters and driving them from the town.
The Syrian army acknowledged that one of its planes had been shot down.
Both Russia and the USA are engaged in military action Islamic State targets in Syria. "We have agreed in the past, that is we and the Russian Federation Pro-Regime Forces, that operations that the coalition were conducting in Syria were effectively degrading ISIS capability and will work to restore that de-confliction chain in the next few hours".
USA forces tangled earlier this month with Syria-allied aircraft in the region. Before that attack, USA officials informed their Russian counterparts.