Officials said the American troops alongside Syrian Democratic Forces were conducting a routine anti-ISIS security patrol near Tal Al-Zahab when they encountered a checkpoint occupied by pro-Syrian regime forces.
"After receiving safe passage from the pro-regime forces, the patrol came under small arms fire from individuals in the vicinity of the checkpoint," Col. Myles B. Caggins III, spokesman for Operation Inherent Resolve, said in a statement. "Coalition troops returned fire in self-defense. The Coalition did not conduct an airstrike. No Coalition casualties occurred."
Caggins said the incident remains under investigation. He did not give any information regarding casualties or injuries to the attackers.
The dustup comes amid reports that a U.S. helicopter gunship attacked a Syrian army checkpoint in the country’s northeast, killing one soldier and wounding two others.
Syrian state media and an opposition war monitoring group reported the attack came after the Syrian army prevented an American convoy from passing through. Syrian state TV said the helicopter attack took place in the village of Tal Dahab, near the town of Qamishli.
The Britain-based Syrian Observatory for Human Rights gave no breakdown of the casualties but said that before the strike, an argument broke out between the Syrian and U.S. troops.
It was not immediately clear if these were the same incidents. The statement by Caggins denies any airstrike by U.S. forces.
Tensions have been rising in northeast Syria between government forces and U.S. troops in recent months. In several instances, Syrian troops prevented U.S. forces from entering several areas in the region.
Hundreds of U.S. troops are stationed in northeastern Syria, working with their local partners from the Kurdish-led Syrian Democratic Forces to fight against the Islamic State group.
The Associated Press contributed to this report.