Special to WorldTribune.com

American intelligence officials say Russia is constructing facilities at a military base in the Syrian port city of Latakia.

The officials reported that Moscow has constructed an air traffic control tower and transported prefabricated housing units for up to 1,000 personnel to an airfield in Latakia, one of the key remaining strongholds of Syrian President Bashar Assad.

Related: Russian boots are on the ground in Syria

Russia has also requested the rights to fly aircraft with military cargo over neighboring countries.

U.S. Secretary of State John Kerry on Sept. 5 called his Russian counterpart, Foreign Minister Sergey Lavrov, to express U.S. concerns.

“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-ISIL coalition operating in Syria,” the U.S. State Department said.

Saudi King Salman, in a meeting with U.S. President Barack Obama on Sept. 4, repeated the Saudi demand that any lasting settlement in Syria would require an end to the Assad regime.

Russian President Vladimir Putin has confirmed that Moscow was already providing some military and logistical support to Syria.

“We are already giving Syria quite serious help with equipment and training soldiers, with our weapons,” Putin said during an economic forum in Vladivostok on Sept. 4, according to the state-owned RIA Novosti news agency.

Syrian state television showed images of an advanced Russian-built armored personnel carrier, the BTR-82a, in combat. Videos also began circulating in which troops shouted orders to one another in Russian.

Last week the Israeli daily Yedioth Ahronoth cited Western diplomatic sources saying that Russia was on the verge of deploying “thousands” of troops to Syria to establish an airbase from which the Russian air force would fly combat sorties against Islamic State of Iraq and Levant (ISIL).

“If they’re moving people in to help the Syrian government fight their own fight, that’s one thing,” a Western diplomatic source told the Los Angeles Times. “But if they’re moving in ground forces and dropping bombs on populated areas, that’s an entirely different matter.”

  Bashar Assad, ISIL, John Kerry, Russian forces said to be building base at Latakia, Syria, Vladimir Putin, WorldTribune.com