Syrian regime said "the flagrant attack" came at a time when it was making a "clear advance in fighting the Daesh terrorist group."
The US-led coalition shot down a Syrian regime jet on Sunday in the southern Raqqa countryside during a combat mission against Daesh, the US military said.
US Central Command said the plane was downed "in collective self-defence of Coalition-partnered forces," identified as fighters of the Syrian Democratic Forces near Tabqah.
The regime confirmed the report, saying the plane crashed and the pilot was missing. It said the incident took place on Sunday afternoon near a village called Rasafah.
The "flagrant attack was an attempt to undermine the efforts of the army as the only effective force capable with its allies ... in fighting terrorism across its territory," it said.
"This comes at a time when the Syrian [regime] army and its allies were making clear advances in fighting the Daesh terrorist group."
The US-led coalition has in recent weeks escalated its aerial bombing campaign in northern Syria and Raqqa province. The US-backed forces have encircled the city of Raqqa and captured several districts from Daesh.
The Syrian regime has also taken territory from retreating Daesh in the western Raqqa countryside and seized back some oil fields and villages that had been under the militants' control for almost three years.