Russian President Vladimir Putin said on Tuesday it was important to avoid actions that might aggravate Syria's civil war, a veiled warning against foreign military intervention or arming anti-government forces.
Russia and the United States are trying to bring the warring sides together at an international conference on ending the bloodshed in Syria, but Moscow is concerned that Washington or other countries might arm the rebels.
"In this crucial period it is extremely important to avoid any actions that could aggravate the situation," Putin said after talks with Israeli Prime Minister Benjamin Netanyahu in the Black Sea resort of Sochi. He gave no further details.
Netanyahu did not immediately make clear whether Putin had eased his concerns that Russia is about to deliver an advanced air defense system to Damascus that could undercut the new diplomatic initiative aimed at reaching a political solution.
Foreign Minister Sergei Lavrov said on Friday that Russia had no new plans to sell the S-300 missile defense system to president Bashar al-Assad's government but left open the possibility they could be delivered under an existing contract.
Reporting by Darya Korsunskaya, Editing by Timothy Heritage