U.S. Secretary of State John Kerry has expressed concern over reports of "an imminent Russian military buildup" in Syria in a September 5 telephone conversation with his Russian counterpart, Sergei Lavrov.
"The secretary made clear that if such reports were accurate, these actions could further escalate the conflict, lead to greater loss of innocent life, increase refugee flows and risk confrontation with the anti-[Islamic State] coalition operating in Syria," the State Department said in a press release.
Kerry and Lavrov agreed that discussions on the Syrian conflict will continue later this month in New York, where the UN General Assembly meets.
Western media reports suggest that Russia may have recently deployed military personnel and aircraft in Syria.
The New York Times reported on September 4, quoting unidentified U.S. administration officials, that Russia has dispatched a military advance team to Syria and has sent prefabricated housing units for hundreds of people to a Syrian airfield and delivered a portable air-traffic-control station there.
The newspaper reported that some U.S. officials said the temporary housing suggested that Russia could deploy as many as 1,000 advisers to the airfield that serves Latakia, Syria's main port city.
The report said that the Russians have filed military overflight requests across bordering countries throughout September.
It added that U.S. officials fear the steps may signal an expansion of Russia’s support for Syrian President Bashar al-Assad.
The Los Angeles Times reported U.S. intelligence had gathered evidence of possible military housing from satellite reconnaissance photos.
Washington has said it is closely monitoring the reports.
Russia has been a close ally of Assad during the Syrian conflict and has provided diplomatic support and military weapons to help Syrian government forces.
Moscow also has a small naval facility at the Syrian port of Tartous on the Mediterranean Sea.