The United States and Germany told Russia that arming President Bashar al-Assad's forces could jeopardise international efforts for a peace conference on Syria.
Secretary of State John Kerry, speaking after talks with his German counterpart Guido Westerwelle, said on Friday Russia's plans to deliver S-300 missiles to Syria were "not helpful" while trying to organise a peace conference to end the conflict.
The missile shipment also posed a threat to Israel's security, he added.
Al Jazeera’s Alan Fisher reports from Washington.
