The US has launched rare air strikes in eastern Syria to thwart an attack on allied Kurdish and Arab fighters by forces aligned to Syria's government.
Another military official, who also spoke on the condition of anonymity, said not all the attacking forces were wearing uniforms, making it more hard to identify them.
The Syrian army, which is supported by Iranian-backed militias and Russian forces, are active on the other side of the river by the city of Deir al-Zor.
Officials say the airstrikes were in defense "of coalition and partner forces".More news: 21 contract HIV after quack reuses syringe
According to reports a headquarters of the Syrian Democratic Forces came under fire from artillery and tanks. But that's been a challenging line for the U.S.to walk as human rights violations stack up against Assad and as his regime's forces threaten US troops and their allies.
The forces were "likely seeking to seize oilfields in Khusham that had been a major source of revenue for Daesh from 2014 to 2017".
United States coalition forces have issued a statement on Wednesday confirming a series of U.S. airstrikes against Syrian pro-government forces along the Euphrates River.
Statements carried by the television stations called it a "new aggression" and "an attempt to support terrorism".More news: Liverpool coach delivers verdict on new signing Tony Gallacher's under-23 debut
The U.S. coalition said in a statement that it launched the strikes in self-defense after as many as 500 attackers began what appeared to be a coordinated assault on an SDF headquarters, where the Turkish forces are accompanied by U.S. troops.
The initial attack happened eight kilometers, or roughly five miles, east of the de-confliction line on the Euphrates River.
Coalition aircraft have also struck regime forces that were perceived as posing a threat to a base at At Tanf, Syria that houses U.S. and coalition military advisers.More news: Dead, At Least 70 injured After Amtrak Train and Freight Train Collide