The Pentagon argued that because they are allied with the Kurds they were free to attack the Syrian plane under the concept of "collective self-defense", and added that they "will not hesitate" to take further military action to defend the Kurds or other partnered forces, from future threats.
Earlier on Sunday, the Syrian army said that "the so-called global alliance today noon targeted the jet over the area of al-Rasafa in the southern countryside of al-Raqqa while it was on a combat mission against the terrorist Daesh", using an Arabic acronym of ISIL, which is also known as ISIS.
Coalition aircraft conducted a "show of force" mission to stop Syrian forces from advancing and coalition officials contacted the Russians on the "de-confliction line' to calm the situation down, but almost two hours later a Syrian SU-22 dropped bombs on SDF fighters, according to Sunday's news release".
A Syrian army statement released on Syrian state television said the plane crashed and the pilot was missing.
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.
"Coalition aircraft conducted a show of force and stopped the initial pro-regime advance toward the SDF-controlled town", the release said. Following the pro-Syrian forces attack, the coalition called its Russian counterparts "to de-escalate the situation and stop the firing", according to the statement.
The shootdown was near the Syrian town of Tabqa.
Earlier this month, a USA jet downed a pro-Syrian government drone that dropped an apparent dud munition near the US -led coalition forces near the southern Syrian town of At Tanf.
"This comes at a time when the Syrian army and its allies were making clear advances in fighting the Daesh (Islamic State) terrorist group". US-backed forces have encircled the city of Raqqa and captured several districts from ISIL fighters. US -led forces have increased their presence at Tanf to deter pro-Syrian government forces in the area.