A coordinated attack was carried out Wednesday against al Tanf, a small U.S. military base in Syria near the border with Jordan, U.S. officials said.
The assault involved "at a minimum" drones and either mortar or rocket fire, a U.S. official told ABC News. No deaths or injuries have been reported.
No one has claimed responsibility for the attack, but Iraqi security officials told ABC News it involved five booby-trapped drones, which are often used by Iranian-backed militias operating in the region.
There are about 1,000 U.S. troops still in Syria as part of efforts to keep the Islamic State from taking back territory. There is a 35-mile buffer zone around the base, as there are Russian and Syrian government troops in the surrounding area.