The United States voiced concerns over Russia’s decision to deploy its most hi-tech air defense system to its base in Syria.

The United States voiced concerns over Russia's decision to deploy its most hi-tech air defense system to its base in Syria.

"It's a capable weapons system that poses a significant threat to anyone," a US official speaking on condition of anonymity told AFP.

"There are significant concerns related to air operations in Syria."

Moscow says it is sending S-400 anti-aircraft missiles to Latakia in northwestern Syria, in a move that comes after Turkey shot down a Russian fighter jet in the border on Tuesday.

The S-400 missiles have a range of about 400 kilometers (250 miles) -- meaning they could reach deep into Turkey or pose a potential threat to US-led coalition planes -- adding yet another dangerous element to an already volatile mix of competing military interests in Syria.

The United States has since August 2014 led a coalition that has flown more than 8,000 bombing runs against positions of the Takfiri group, ISIL(so-called Islamic State in Iraq and Levant) in Syria and Iraq.

Russia, too, is targeting the Takfiri insurgents in Syria, under the request of Damascus, but these are mainly in different parts of the country from where US and coalition planes are flying.   

Though Russia and the US-led coalition have agreed on a set of guidelines aimed at ensuring pilots stay out of each other's way, the prospect of batteries of Russian anti-aircraft missiles arriving in Syria is nonetheless raising eyebrows in the Pentagon.

But another US official, also speaking anonymously, said the S-400s "shouldn't" affect coalition flights.

"We are not going to interfere with (the Russians') operations and they are not going to interfere with ours. There's no reason for us to be targeting each other," the official said.

He also noted that Russia in the past week has delivered more than 30 T-90 and T-72 tanks to Latakia.