WASHINGTON (Reuters) - The United States shot down a pro-Syrian government drone that fired toward U.S.-led coalition forces in Syria on Thursday, a U.S. military spokesman said, in a major escalation of tensions between Washington and troops supporting Damascus.

The armed drone “hit dirt” and there were no injuries or damage done to the coalition patrol in southern Syria. But U.S. Army Colonel Ryan Dillon, a spokesman for the U.S.-led coalition fighting Islamic State, told reporters the drone meant to attack them and dismissed the possibility it had fired a warning shot.

“This clearly showed a threat even if it were a warning shot; it was something that showed a hostile intent, a hostile action and posed a threat to our forces because this drone still had munitions that were still on it,” Dillon said.

He added that it was the first known time that pro-Syrian government forces had fired at coalition forces in the area.

A U.S. official, speaking on condition of anonymity, said the munition landed a few hundred yards from coalition forces and failed to explode. The official added that a U.S. F-15 fighter jet was used to strike the drone, which was likely Iranian-made but that further analysis was being carried out.

Dillon said the United States had earlier in the day carried out a strike against two pro-Syrian government pick-up trucks with weapons that had moved against U.S.-backed fighters near the southern town of At Tanf.

It was the third such strike, and the second this week, by the Pentagon, which has sought to stay out of Syria’s civil war to focus firepower instead on Islamic State in Syria and Iraq.

The concern is that such strikes could take away attention from the fight against Islamic State militants.

“Unfortunately, there have been (these) incidents that have taken our focus away from fighting ISIS,” Dillon said, using an acronym for Islamic State.

The Syrian Democratic Forces (SDF) launched their assault to capture Raqqa, Islamic State’s de facto Syrian capital.

For months, air strikes and special forces from the U.S.-led coalition have helped them encircle Raqqa, which Islamic State seized in 2014 and has used as a base to plan attacks abroad.

On Tuesday, the United States launched an air strike against Iranian-backed fighters who it said posed a threat to U.S. and U.S.-backed forces in southern Syria.

A military alliance fighting in support of President Bashar al-Assad threatened on Wednesday to hit U.S. positions in Syria, warning its “self-restraint” over U.S. air strikes would end if Washington crossed “red lines”.

In recent days, the U.S. military has repeatedly warned massing forces to stay away from a ‘deconfliction zone’ near a garrison used by American special forces and U.S.-backed fighters around At Tanf.

The zone was agreed with Russia, Syrian President Bashar al Assad’s ally. Assad is also backed by Iran and Shi’ite militias.

Tanf is part of a region known as the Badia, a vast, sparsely populated desert territory that stretches to the Jordanian and Iraqi borders and was declared a military priority by Syria’s foreign minister in May.