Russia is trying to convince Iran to withdraw a lawsuit against the cancellation of a contract to supply Iran with S-300-PMU1 (NATO: SA-10) Surface-to-Air Missile (SAM) Air Defense Systems. So far, the efforts have not been successful.
In 2007, Iran and Russia signed a $800 million contract for the delivery of five S-300-PMU1 battalions. In 2010, this contract was cancelled by Russia due to UN Security Council Resolution 1929.
This resolution bans the supply to Iran of conventional weapons, including missiles, tanks, attack helicopters, warplanes and ships. However, Iran is convinced that the S-300 SAM is exempt because they are considered defensive weapons.
Iran then proceeded in 2011 to file a $4 billion lawsuit against Russia in an international arbitration court in Switzerland. Iran has states that it will only withdraw the lawsuit if Russia fulfills the terms of the contract.
Meanwhile, Russia is sending mix signals about the delivery of S-300 SAM systems to Syria. Delivery of the S-300 systems is scheduled to begin in the very near future.
However, Russia has stated that it is willing to delay deliveries under the condition that the West complies with some of Russia's demands regarding Syria.
Russia has also warned that it could accelerate deliveries of the S-300 if its demands are not met. From its standpoint, Syria could use the S-300 to defend itself against foreign aggression.
With Russia using deliveries of the S-300 as a negotiating tactic, Israel for its part has stated that it reserves the right to prevent Syria from receiving any new weapons, including the S-300, by force if necessary.