Defense Secretary Ash Carter had a 50-minute conversation with his Russian counterpart over Moscow's military buildup in Syria.

Pentagon press secretary Peter Cook says Carter and Russian Defense Minister Sergei Shoigu had a constructive discussion and talked about areas where the interests of their countries converge.

Cook says the two men agreed to talk more about how to deconflict the U.S. and coalition military campaign against Islamic State militants in Syria with Russia's recent moves to send equipment and personnel to the government of Syrian President Bashar Assad.

The U.S. has called for Assad to step down and the Russian military aid works against that aim.

U.S.-Russian military relations were suspended after Russia annexed the Crimea region of Ukraine, but that does not disallow conversations between leaders.