Russia has sent sophisticated anti-ship missiles to Syria, US media report.
The New York Times quotes unnamed US officials as saying the missiles could be used to counter any potential future foreign military intervention in Syria.
Without confirming details, Russia’s foreign minister said Russian supplies did not break any international rules.
It comes amid growing alarm that chemical weapons may be being used in Syria, something US President Barack Obama has said would be “a red line”.
Meanwhile efforts continue to arrange an international conference on Syria.
The United Nations Secretary General Ban Ki-moon met Mr Lavrov in Sochi on Friday to discuss the plans for the conference, which would aim to bring together the Syrian opposition and members of President Bashar al-Assad’s government.