The pro-government forces had been backed by artillery, tanks and other heavy weaponry when they attacked an SDF headquarters "eight kilometres [5 miles] east of the agreed-upon Euphrates River de-confliction line", U.S. officials said.
CNN initially reported that more than 100 pro-regime fighters were killed in the coalition counter-attack, but Veale said there is no estimate of enemy casualties at this time. Russian officials assured the Coalition they would not engage coalition forces in the vicinity. Initial media reports, citing unnamed U.S. officials, suggested that some 100 Syrian soldiers had died in the assault by the coalition forces.
One U.S. -backed SDF fighter was wounded in the exchange of strikes.
The forces were "likely seeking to seize oilfields in Khusham that had been a major source of revenue for [IS] from 2014 to 2017, the official said".
The Pentagon said it was not looking for conflict with the Syrian regime, Reuters reported. Syrian forces control the western side of the line, and the SDF controls the eastern side of the line.
"The military goal is to defeat ISIS in Syria", White said.
Pro-Syrian government fighters had alleged tried to take and area that is being controlled by the SDF forces east of the River Euphrates since it liberated the region from the Islamic State in September 2017.
North Korea has 'no intention' of holding talks with US at Games
He had stopped in Japan ahead of attending the opening ceremony of the Pyeongchang Winter Olympics in South Korea on Friday. When asked by reporters if he would be willing to have some sort of interaction, Pence had said "we'll see what happens".
According to the Syrian Observatory for Human Rights, which only confirmed 45 dead among pro-regime forces, the initial attack took place near Khasham.
And while the USA -led coalition mission hasn't changed and ISIS is on the run, work remains to be done, she said.
The U.S. -led coalition responded with "AC-130 gunships, F-15s, F-22s, Army Apache helicopter gunships and Marine Corps artillery", according to Fox News reporter Lucas Tomlinson.
"Coalition officials were in regular communication with Russian counterparts before, during and after the thwarted PRF [pro-regime forces] attack", Veale said.
As a result, 25 members of the pro-government unit were injured. "The incident was caused by uncoordinated reconnaissance and search operations plans of the Syrian militias with the Russian command task force in the locality of Salhiyah".
About 2000 USA forces remain on the ground in Syria, allied to the Kurdish-led SDF alliance. Russia's foreign ministry said the USA was attempting to secure Syrian resources. In June, the coalition shot down a Syrian warplane near Raqqa, accusing it of getting too close to its local ground forces.
"Russia was invited to Syria by the legitimate government to help defeat the terrorists, and we did so since 2015".
US Marines firing a howitzer in Syria.