18 killed in suspected Turkish strikes in Syria

The deployment immediately raised questions in the Pentagon, which wondered about its goal. Russian Federation is interested in propping up Assad in part because Russia's only naval facility outside the former Soviet Union is on the Syrian coast.

"The S-300 is a purely defensive system and poses no threat to anyone", said defense ministry spokesman Igor Konashenkov.

As well as operating a naval facility in Tartus, Russia runs an air base outside the Syrian coastal city of Latakia, which now houses warplanes used in its bombing campaign in support of ally Assad.

The S-300 deployment was announced a day after the USA announced it was suspending direct diplomatic contacts with Russian Federation on ending the war in Syria.

A Syria missile system deployed by Russian Federation could deny the USA the use of warplanes and cruise missiles to counter a stepped up offensive in the rebel-held east around Aleppo since the collapse of a cease-fire two weeks ago.

It has also created new friction between the United States, which backs some rebel groups, and Russian Federation, which supports President Bashar al-Assad and led to Washington breaking off talks with Moscow over renewing the ceasefire.

Amid the rising U.S.

"The missile battery is meant to ensure the safety of the naval base".

According to reporting by the AP on other developments in Syria, forces backing Syrian President Bashar Assad pressed their offensive Tuesday on Aleppo's rebel-held zone from the south, after capturing areas on other fronts in recent days. Damascus said 60 Syrian soldiers died in the air raid.

The suspension in Syria talks was announced just hours after the Kremlin said Russian President Vladimir Putin had signed a decree halting a joint program with the US on the disposal of weapons grade plutonium.

The S-300, a sophisticated long-range system capable of striking enemy aircraft and cruise missiles up to 250 kilometers (155 miles) away, could cover other areas in Syria along with Tartus.

The village is in an area controlled by the Islamic State militants.

"I would question just what the objective of the system is", Cook said.

The Russian Foreign Ministry said the US has "done all it could to destroy the atmosphere encouraging cooperation".

Konashenkov sought to down play the deployment, saying "the S-300 is exclusively a defensive system that doesn't threaten anyone".

Baluyevsky, commenting on statements from American experts, who said that Russia's battery of S-300 was directed against North Atlantic Treaty Organisation aircraft, said that such estimates were "not groundless".

In a sharp attack on Washington, Konashenkov also charged that the USA -led action against the Islamic State group was merely an "imitation" that has failed to prevent the IS expansion.

According to a senior US official, the Pentagon has ordered troops who had been deployed to set up the joint implementation center - fewer than 20 - to return to their bases. -Russian truce in Syria.

The Obama administration said it made a decision to cut off discussions on Syria because Russia had not lived up to the terms of last month's agreement to restore a tattered cease-fire and ensure sustained deliveries of humanitarian aid to besieged cities, such as Aleppo, which has been under bombardment from Russian and Syrian forces.