The statement underlined high tensions between Moscow and Washington after the collapse of a US-Russia-brokered Syria truce and the Syrian army advancing in Aleppo backed by Russian warplanes.

Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said any US strikes on areas controlled by Syrian President Bashar Assad's Army could jeopardize the lives of Russian servicemen.

He said Moscow was worried by media reports saying that Washington was considering the possibility of striking Syrian army positions.

'I would recommend our colleagues in Washington to carefully weigh possible consequences of the fulfillment of such plans,' Konashenkov said.

Russia said it was unhappy with the US-led coalition's air raid on Syrian army positions near Deir el-Zour that killed 60 Syrian soldiers on September 17, rejecting the explanation from the American side that the attack was a mistake.

Konashenkov said 'we have taken all the necessary measures to prevent any such 'mistakes' with regard to Russian servicemen and military facilities in Syria.'

In Washington, State Department spokesman John Kirby said 'We're looking at the full range of options….

He said the range of Russia's S-300 and S-400 air defense missile systems deployed to Syria would be a 'surprise' to any country operating its aircraft over the country.

Konashenkov added that the Syrian army also has various Soviet- and Russian-built air defense missile systems, which have undergone modernization over the past year.

Konashenkov warned, however, that the Russian military won't have time to use the hotline if it sees missiles on their way to targets in Syria.

'It must be understood that Russian air defense missile crews will unlikely have time to clarify via the hotline the exact flight program of the missiles or the ownership of their carriers,' he added.

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