Story highlights The drone was downed north of At Tanf, just outside the 55 kilometer de-confliction zone

One official said that the drone was shot down because it was "assessed to be a threat"

(CNN) A US F-15E fighter jet shot down a pro-Syrian regime drone near At Tanf, Syria, on Monday, two US officials told CNN, the third downing of a pro-regime aircraft this month.

The US-led international coalition later confirmed the incident in a statement, saying the armed drone was downed "after it displayed hostile intent and advanced on Coalition forces" that "were manning an established combat outpost to the northeast of At Tanf where they are training and advising partner ground forces in the fight against ISIS."

The drone was downed just outside the 55 kilometer de-confliction zone, according to the officials.

It was an Iranian-made Shahed 129 and was thought to be armed and in firing range of US troops.

One official said that the drone was shot down because it was "assessed to be a threat."

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