A US military spokesman said the United States launched air and artillery strikes after Syrian government forces attacked a compound belonging to the Syrian Democratic Forces, a USA ally, in Khusham, Syria, Politico reported.
US forces reportedly responded to an "unprovoked attack" by Syrian pro-regime forces at the Syrian Democratic Forces (SDF) headquarters on Wednesday, according to a statement from US Central Command (CENTCOM).
No US service personnel were injured or killed but one SDF member was wounded.
The flare-up lasted into the small hours of Thursday and was sparked by an attack on positions held by the Kurdish-led Syrian Democratic Forces (SDF) in Deir Ezzor province.
US and Kurdish forces responded to that skirmish with air and artillery strikes, the official said.
The attack on the SDF headquarters east of the Euphrates River was well coordinated and involved T-54 and T-72 tanks, as well as artillery.
Officials say the airstrikes were in defense "of coalition and partner forces".
"The coalition conducted strikes against attacking forces to repeal the act of aggression", it said.
US officials said no Americans were injured or killed in the attack by the pro-regime forces.
A rare USA airstrike in Syria has killed approximately 100 pro-government troops.
Officials said no US troops were injured or killed. The YPG is one of many groups that makes up the SDF.
With the defeat of Islamic State in most of Syria the coalition and the Syrian regime share a long "de-confliction" line mostly along the Euphrates river.
Coalition officials were in regular contact with their Russian counterparts before, during and after the attack, who had assured them that they would not target U.S. and SDF forces in the area.