The defense chiefs of Russia and the United States spoke for the first time in more than a year on September 18 to discuss the conflict in Syria.
They spoke as Moscow's deepening military buildup has raised the prospects of possible coordination in the fight against Islamic State militants as well as potential conflict between Russian forces and a U.S.-led coalition.
The Pentagon said the 50-minute phone call between U.S. Defense Secretary Ash Carter and Russian Defense Minister Sergei Shoigu included an agreement for further U.S.-Russian talks about how to keep their militaries out of each other's way -- something known as "deconfliction" in military terminology.
High-level military talks with Moscow were severed by the Pentagon in 2014 over Russia's annexation of Crimea and intervention in eastern Ukraine.
Russia's buildup at Syria's Latakia air base raises the possibility of simultaneous U.S. and Russian air combat missions in Syrian airspace.
U.S. officials say Russia has moved fighter jets to Syria as part of its growing military force in the country.
The officials told Reuters and The Wall Street Journal on September 18 that Russia has moved at least four tactical fighter jets to the airfield near Syria's Mediterranian port of Latakia.
Other reports said Russia has sent at least four attack helicopters and some transport helicopters to the airfield during the previous 24 hours, bolstering earlier deployments of Russian helicopters made since September 4.
Three Russian Navy amphibious assault ships also have crossed through the Bosphorus Strait from the Black Sea to the Mediterranean Sea in recent days.
Russia, a staunch ally of Syrian President Bashar al-Assad, also has sent T-90 tanks, heavy artillery, antiaircraft missiles, and hundreds of troops to Syria.
The buildup has worried Washington, which says it fears Moscow’s goals are aimed at supporting Assad’s regime rather than defeating IS fighters.
In London on September 18, U.S. Secretary of State John Kerry said that U.S. President Barack Obama believes military-to-military conversations with Moscow are “an important next step.”
Kerry said the U.S. focus “remains on destroying” the Islamic State group and encouraging a political settlement to Syria’s civil war.
White House spokesman Josh Earnest said on September 17 that Washington is open to “tactical, practical” discussions with Russia about cooperating against IS militants in Syria.
But he said a political solution to Syria’s civil war is not possible as long as Assad remains in power, and that Russia should not try to prop up Assad’s regime.
Russian Foreign Minister Sergei Lavrov suggested to Kerry earlier this week that there should be direct military-to-military talks to coordinate action in Syria.
Earnest told reporters at the White House that the U.S. administration welcomes “constructive contributions from the Russians” in the fight against IS militants, also known as ISIL.
“So that’s why we’ll remain to open to tactical, practical discussions with the Russians in order to further the goals of the anti-ISIL coalition and ensure the safe conduct of coalition operations,” he said.
“We’ve made clear that Russia’s military actions inside of Syria, if they are used to prop up the Assad regime, would be destabilizing and counterproductive,” Earnest added. “Propping up a regime that’s losing its grip on power, in many cases, only has the effect of driving more Syrians into the arms of extremists."
Earnest said that there is “no military solution to the turmoil that plagues Syria right now.”