This Friday, April 28, 2017, still taken from video, shows U.S. forces patrolling on a rural road in the village of Darbasiyah, in northern Syria. U.S. armored vehicles are deploying in areas in northern Syria along the tense border with Turkey, a few days after a Turkish airstrike that killed 20 U.S.-backed Kurdish fighters, a Syrian war monitor and Kurdish activists said Friday.
Photo Credit: AP Photo via APTV
But soon afterward, more pro-Assad forces began entering the area with anti-aircraft weapons and bulldozers that the coalition said were not part of the agreement or needed to treat or remove the wounded. The coalition issued warnings through its "de-confliction" line with Russia, but the official said those were ignored.
The U.S. doesn't speak directly with Assad's government, which it accuses of various atrocities over more than six years of civil war. Instead, it addresses problems with Syria indirectly, usually through Russian officials. Russia is a military ally of Assad's government.
According to a coalition statement, at least 60 pro-Assad forces were about 40 kilometers (25 miles) from the coalition training area at Tanf, which is inside a protected zone near Syria's southern border with Jordan. A number of the forces have been in that area since a previous U.S. airstrike on pro-Assad forces on May 18.
A second U.S. official said American airstrikes destroyed two artillery pieces and an anti-aircraft weapon and damaged a tank in Tuesday's attack. It wasn't clear how many forces were killed, said the official, who also was not authorized to discuss details of the operation publicly and spoke on condition of anonymity.
Officials said some pro-Assad forces likely remain in the area. It wasn't clear how many are there or if they might be preparing to leave.
U.S. officials haven't identified the forces exactly, but have described them as backed or directed by Iran. It's not clear if they're Iranian soldiers, Hezbollah members, Syrian troops or part of another militia.
The region around Tanf, where the borders of Jordan, Syria and Iraq meet, has been considered a de-conflicted zone under an agreement between the U.S. and Russia. The coalition uses the base to train Syrian rebels in the fight against ISIS.
The U.S. dropped 90,000 brightly-colored leaflets more than a week ago, warning pro-Assad forces to leave the area and saying the coalition would take steps to defend itself.