The incident came as a monitoring group reported the first ground fighting between Syrian regime troops and the US-backed alliance of Kurdish and Arab fighters.
Downing the Syrian warplane comes as the Syrian army is advancing against IS in the southern and western countryside of Raqqa, while the US -backed Syrian Democratic Forces (SDF) are fighting IS inside Raqqa, the de facto capital of IS.
The U.S. -led coalition headquarters in Iraq said in a written statement that a U.S. F-18 Super Hornet shot down a Syrian government SU-22 after it dropped bombs near the U.S. partner forces, known as the Syrian Democratic Forces. "The coalition does not seek to fight Syrian regime, Russian, or pro-regime forces partnered with them, but will not hesitate to defend coalition or partner forces from any threat".
US -led jets stopped the fighting by flying close to the ground and at low-speed in what is called a "show of force", the Pentagon said.
Following the strike, the coalition alerted Russian counterparts to de-escalate the situation. US-backed forces have encircled the city of Raqqa and captured several districts from ISIL fighters.
The U.S. move is not the first, as U.S. forces struck Syrian military positions in the Syrian desert, where the Syrian army was advancing against IS and becoming close to the Tanf border crossing with Iraq, where USA and British military positions were installed.
A U.S. Navy fighter jet shot down a Syrian regime fighter jet on Sunday that had dropped bombs on Syrian rebel forces fighting ISIS in Syria. US -led forces have increased their presence at Tanf to deter pro-Syrian government forces in the area.