The Aviationist via Filip Modrzejewski/Foto Poork A US aircraft shot down a large drone piloted by pro-regime forces after it dropped "one of several weapons" near coalition forces in Syria, the Pentagon said in a statement on Thursday.

The Pentagon said the drone aircraft was similar in size to an MQ-1 Predator, which has a wingspan of 55 feet and weighs more than 1,000 pounds.

The statement did not specify what type of US aircraft was involved during the incident, which occurred in southern Syria.

Unmanned aerial vehicles have become a fixture on the battlefield in Syria, as both the US, Syria, Iran, and Russia all have operated weaponized and unarmed surveillance drones there. The Islamic State has also built their own makeshift drones, which have been used to harass coalition troops.

The incident on Thursday, however, came soon after the US had to destroy two "pro-regime armed technical vehicles" — a term that usually describes trucks outfitted with machine guns or other heavy weapons — that had advanced toward coalition troops in the deconfliction zone at At Tanf.

Such incidents are troublesome, given the Pentagon's reliance on local partners to conduct much of the fight against ISIS, and the risk of getting bogged down in open conflict with others in the conflict.

"As long as pro-regime forces are oriented toward Coalition and partnered forces the potential for conflict is escalated. Coalition forces are oriented on ISIS in the Euphrates River Valley," the statement said. "The Coalition calls on all parties to focus their efforts in the same direction to defeat ISIS, which is our common enemy and the greatest threat to regional and worldwide peace and security."