Warplanes from the US-led coalition operating over Syrian airspace west of the Euphrates River will be treated as potential targets, Russia's Defence Ministry said on Monday, a day after the US military shot down a Syrian air force jet.
Russia, Syria's main ally, also said it is suspending a cooperative pact with the US aimed at maintaining airspace safety in Syria, BBC reported.
The latest spat came a day after an American F18E Super Hornet fighter jet downed on Sunday a Syrian SU-22 which was targeting areas held by a US-backed Syrian Democratic Forces (SDF), a Kurdish-Arab coalition militia fighting the Islamic State in the city of Raqqa.
Syria condemned America's "flagrant attack", saying it would have "dangerous repercussions".
"Any aircraft, including planes and drones belonging to the international coalition operating west of the Euphrates river, will be tracked by Russian anti-aircraft forces in the sky and on the ground and treated as targets," the ministry said.
The memorandum had been in place to avoid incidents occurring between the US and Russian air forces, both of which conduct parallel aerial operations over Syria as they offer support to distinct native forces on the ground.
Russia decried the downing as "cynical" and accused the international coalition of failing to use the appropriate communications channels that would have resolved the situation, Efe news reported.
The ministry insisted that the SU-22 jet had been on a mission in Syrian government airspace.
The Pentagon said, however, that the bombing against the SDF in Taqba, to the west of Raqqa, occurred in spite of US warnings.
The Pentagon said that it did not seek to fight the Syrian regime, Russia or pro-regime forces, but was merely acting in defence of its coalition partners in Syria.
A host of international parties are embroiled in the Syrian civil war to varying degrees, with Russia and Iran aiding Syrian President Bashar al-Assad, who receives further ground support from Lebanese Shia militia Hezbollah.
Meanwhile, Turkey backs members of the Free Syrian Army in the provinces backing onto the Turkish border.
The US uses airstrikes to clear the way for the SDF in Syria amid a huge onslaught to re-capture the IS's self-proclaimed regional capital Raqqa.