Lack of Combat Air Controllers on the ground and relying on the Russians.
Via Fox News:
The Obama administration expressed its “regret” Saturday for an airstrike that mistakenly killed Syrian forces, a senior administration official told Fox News, as the U.S. awaited a response from the Assad regime.
The U.S. military halted its air raid against the Islamic State terror group in eastern Syria after learning it struck the Syrian military, a U.S. Central Command official confirmed. The CENTCOM official said the U.S. military was “certain” about the outcome of the strike. Officials had been watching these forces “for a few days” thinking they were ISIS.
Syria and Russia said the U.S.-led coalition had struck a Syrian military base in Deir el-Zour that was surrounded by ISIS fighters, enabling them to advance. The U.S. is not known to have directly struck Syrian President Bashar Assad’s forces at any point during the five-year civil war.
The CENTCOM official described the target as “irregular forces,” adding that multiple U.S. aircraft struck six military “troop carrier” vehicles and one tank which were “out in the open.” The U.S. military informed Russian counterparts before the strike but “did not share specifics” of the target, just the airspace and general area.
A Russian Defense Ministry official said Syria has informed them that 62 of its soldiers were killed in the airstrike. Russia has been waging a year-old air campaign on behalf of Assad’s forces and closely coordinates with them.
The CENTCOM official said the U.S. was making calls to Russia through diplomatic channels.
The CENTCOM statement read, “the airstrike was halted immediately when coalition officials were informed by Russian officials that it was possible the personnel and vehicles targeted were part of the Syrian military.”
It added, “coalition forces would not intentionally strike a known Syrian military unit.”[…]
Earlier on Saturday, Russian President Vladimir Putin questioned the U.S. commitment to the fragile cease-fire, suggesting that Washington wasn’t prepared to break with “terrorist elements” battling Assad’s forces.
Russia has accused Washington of failing to rein in the rebels, and on Saturday Putin asked why the United States has insisted on not releasing a written copy of the agreement. Officials have provided details of the agreement in press conferences, but have not released an official document, fueling suspicions on both sides.
“This comes from the problems the U.S. is facing on the Syrian track — they still cannot separate the so-called healthy part of the opposition from the half-criminal and terrorist elements,” Putin said during a trip to Kyrgyzstan.