The U.S. military says it shot down a Syrian Air Force jet that dropped bombs near U.S.-backed forces in the fight against Islamic State militants in Iraq and Syria.According to a statement from the Pentagon, pro-Syrian regime forces attacked a Syrian Democratic Forces-controlled town West of Raqqa, the de facto ISIS capital the rebel fighters were trying to take back. The bombings wounded "a number of SDF fighters and driving the SDF from the town."Two hours later, the U.S. Military said it shot down the Syrian warplane, acting "in collective self-defense of Coalition partnered forces."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 Coalition's mission is to defeat ISIS in Iraq and Syria," the Pentagon added. "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. "But Sunday's event signals the mounting conflict in the region, as the U.S. tries to defeat the Islamic State in the eastern part of the country, as NPR's Tom Bowman reports: