Secretary of State John Kerry spoke Saturday with his Russian counterpart to discuss concerns over reports that Moscow is increasing its military presence in war-torn Syria.
Kerry spoke by phone with Russian Foreign Minister Sergei Lavrov, according to the State Department, to discuss Syria, "including U.S. concerns about reports suggesting an imminent enhanced Russian military build-up there."
In recent days, a number of media reports have suggested Russian President Vladimir Putin is increasing his military support for embattled Syrian President Bashar al-Assad, whose country has been in a state of civil war since 2011.
Russia has reportedly constructed an air traffic control tower and portable housing units for military personnel in the Syrian port city of Latakia, according to the New York Times and Telegraph newspapers.
The Times reported that officials believe the housing may be for Russian military adversers or personnel.
Officials told the newspaper that Russians may use the site as a hub to deliver military supplies to Assad's forces, or even as a base from which to launch airstrikes.
In the telephone call Saturday, the State Department said Kerry "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-ISIS] Coalition operating in Syria."
In his press briefing on Thursday, State Department spokesperson Mark Toner told reporters officials had been looking into the reports.
"We’re unclear what these might be intended for or whether this is actually happening," Toner said, "but certainly, we would be concerned by any attempt to support the Assad regime with military personnel, with aircraft, with supplies of any kind, or funding, because we view it as destabilizing and counterproductive."
Moscow has been a staunch backer of the Assad regime since Syria first descended into chaos into several years ago, shipping weapons to Damascus and defending the Syrian president on the international stage.