PENTAGON - Islamic State militants captured heavy military weapons, possibly including air defense equipment, when they retook the Syrian town of Palmyra from Syrian and Russian forces, according to the U.S. general leading the fight against the terror group.

“I think they (Russia and Syria)… probably took their eye off the ball in Palmyra because they were so focused on Aleppo, and they didn't properly secure their gains,” Lt. Gen. Stephen Townsend told Pentagon reporters via teleconference Wednesday.

Townsend said the terror group took armored vehicles, various guns and other heavy weapons during the assault. He said they also might have taken air defense weapons, which could be used to target coalition aircraft carrying out air strikes against the group.

Syrian and Russian forces likely will push to retake Palmyra soon, but if those forces fail to act, the U.S. will strike Islamic State there, according to Townsend.

“We will do what we need to do to defend ourselves,” the general said.

A view of equipment in a Russian base in what is s A view of equipment in a Russian base in what is said to be Palmyra, Syria in this still image taken from video uploaded to social media on Dec. 13, 2016. A view of equipment in a Russian base in what is said to be Palmyra, Syria in this still image taken from video uploaded to social media on Dec. 13, 2016.

There are two factors complicating any coalition involvement in pushing IS out of Palmyra, according to Townsend. The first is that the area was originally taken by the Russians and Syrians, not the coalition. A movement on Palmyra would need to be deconflicted with the Russians to prevent any potential mishaps in the air.

The second factor, according to Townsend, is that the coalition is “not sure" who is where on the ground.

“We can't tell one side from the other, so we can't tell if the truck and the armored vehicle is being operated by a regime trooper, a Russian trooper or ISIL fighter," he said, using a common acronym for Islamic State.

Until that can be sorted out, he said, the U.S. is using “common sense” to stay out of Palmyra while protecting coalition interests.