美关注俄在叙利亚布置S-400（英）

The US military is very concerned about Russia’s imminent deployment of an advanced missile defense system to Syria, an American official says.

The Kremlin has announced that it is sending S-400 anti-aircraft missiles to Latakia in northwestern Syria in the wake of shooting down a Russian warplane inside Syria by Turkish jets on Tuesday.

A US official, speaking on condition of anonymity, said on Wednesday the S-400 poses a significant threat. He said the planned deployment is raising “significant concerns” for the US military, which is conducting airstrikes in Syria.

"It's a capable weapons system that poses a significant threat to anyone," the official told AFP. "There are significant concerns related to air operations in Syria."

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

On Tuesday, NATO member Turkey shot down a Russian Sukhoi Su-24 Fencer jet, claiming the aircraft had repeatedly violated its air space.

Russian President Vladimir Putin said the jet had been attacked when it was 1 kilometer inside Syria. He warned of "serious consequences" and called it a “stab in the back” administered by "the accomplices of terrorists."

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

One pilot who survived from the jet crash told Russian state television that his aircraft had received no warnings and had not violated Turkish airspace.

Syrian special forces working with the Lebanese resistance movement Hezbollah rescued Konstantin Murakhtin after he parachuted from the aircraft.

He said he knew exactly the plane’s location when it came under fire. “Our entire flight, to the moment we were attacked, was under my command.