CNN
)CNN)Defense Secretary Ash Carter said Thursday that the Pentagon is looking into an incident in which U.S. support jets assisting Syrian rebels diverted to Iraq to strike suspected ISIS militants last week, leaving the rebels without badly needed air cover.
Speaking to reporters on a flight to Warsaw, Poland, for a NATO meeting, Carter said the review will "see if there are any lessons learned."
One aircraft flying air support missions over Al-Bukamal during the recent fighting there was called off and diverted to strike at a massive convoy of suspected ISIS militants that had been observed to be trying to leave the southern outskirts of Fallujah, according to a senior U.S. official. Several aircraft were diverted from various patrols in different parts of Iraq, but only one was taken away from the Al-Bukamal battle.
Carter said the U.S.-backed fighters have moved back in since being pushed back by ISIS. "Those forces have regrouped and are back in the fight," Carter said. He added that they didn't anticipate how quickly things would develop in Fallujah. "In this case, they were adjusting to another very successful set of airstrikes in Fallujah," he said.
It's not clear when and if other aircraft were sent to Al-Bukamal, but it left fighters of the U.S.-backed and Pentagon-trained New Syrian Army without the air cover needed in the Al-Bukamal area as ISIS staged a counterattack on the ground.
Several New Syrian Army fighters were killed and wounded, according to U.S. officials.
The battle for Al-Bukamal has now continued for several days indicating both the strength of ISIS in the area to dominate civilians and the lack of capability by the New Syrian Army. U.S. defense officials had touted the fight for Al-Bukamal as a potential success for the New Syrian Army forces the U.S. has trained and backed, but in the wake of the ISIS counterattack, officials now acknowledge the National Security Agency has slowed down its operations there, because of the strength of the ISIS presence.
U.S. officials believe that some New Syrian Army weapons and equipment have likely fallen into ISIS hands as the New Syrian Army fighters retreated.
"We clearly didn't get everything because we saw Daesh displaying equipment that had been left behind by the New Syrian Army as it pulled out of the area," Col. Christopher Garver, spokesman for Operation Inherent Resolve, said.