Jeff Davis, a Pentagon spokesman admitted that advanced Russian air defense systems have complicated the situation for the US-led coalition over the skies in Syria, BloombergView reported on Thursday.

Russia deployed its S-400 air defense missile system to the Syrian city of Latakia in the wake of Turkey’s shooting down of its warplane over the Arab country last month.

The S-400 has a range of about 400 kilometers and can destroy tactical and strategic aircraft as well as ballistic and cruise missiles.

The move has ignited a debate in Washington on how to respond, said another administration official, the report added.

The US government could decide to resume flights in support of what it calls “moderate” militants, but that could risk a deadly incident with the Russian military, the official added.

The administration official noted that Russians are aiming to keep American-manned flights out of the skies over certain parts of Syria and Washington seems to have agreed “to their rules of the game."

Shortly after the system’s deployment to Syria in November, an unnamed US official expressed concern over the move, saying, "It is a capable weapons system that poses a significant threat to anyone."

Russia has been conducting airstrikes on Daesh at the request of the Syrian government since September 30.

US warplanes have also been conducting airstrikes against purported ISIL positions in Syria since last year; Press TV reported.

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