The U.S. military said on Thursday it had bolstered its "combat power" in southern Syria, warning that it viewed Iran-backed fighters in the area as a threat to nearby coalition troops fighting Islamic State.
The remarks by a Baghdad-based spokesman for the U.S.-led coalition battling Islamic State was the latest sign of tension in the region, where the United States has forces at the base around the Syrian town of At Tanf supporting local fighters.
"We have increased our presence and our footprint and prepared for any threat that is presented by the pro-regime forces," said the spokesman, U.S. Army Colonel Ryan Dillon, referring to Iran-backed forces supporting Syrian President Bashar al-Assad.
Dillon estimated that a small number of Iran-backed forces had remained inside a so-called "deconfliction" zone meant to ensure the safety of U.S.-led coalition forces since a May 18 U.S. strike on their advancing formation.
Meanwhile, a larger number had been massing directly outside the zone, which was agreed between the United States and Russia, which is supporting Assad.