SEVASTOPOL, August 19. /TASS/. The US sanctions against Iran are no concern of Russia, Russian Foreign Minister Sergey Lavrov said on Wednesday, answering a question whether the possible sale of S-300 air defense systems to Iran by Russia fell within the scope of US sanctions laws.

"The US sanctions are no concern of ours. We only fulfill our international obligations, above all, with regard to sanctions, this is the decision of the UN Security Council. All other unilateral restrictions imposed bypassing the Security Council in violation of the general norms of the international law are of no interest to us. So, let our American colleagues study the issue, perhaps, it will useful for them to come to the conclusion that far from all corresponds to their vision of international law," Lavrov said.

On August 14, Russian Deputy Foreign Minister Sergey Ryabkov said that "the decision on possibly supplying S-300 to Iran has already been made by the Russian president, and technical issues of this matter are being discussed." "This is an exclusively bilateral issue. Participation of third countries is not envisaged and is not required," he stressed.

Russia’s Defense Ministry earlier said Moscow was ready to hand over to Tehran the modernized versions of S-300. Russia is currently working to upgrade the missile defense system in line with the Iranian side’s recommendations.

The ministry said these missile systems may be delivered to Iran under the Russian presidential decree "immediately."

Russian President Vladimir Putin lifted the ban on the S-300 supplies to Iran in April 2015 when six world powers confirmed significant progress after talks with Iran on the nuclear program in Lausanne, Switzerland.

Under the 2007 contract, Moscow pledged to deliver to Tehran five battalions of S-300 medium-range air defense systems worth $800 million. Iran made an advance payment of $166.8 million. No supplies followed up to the middle of 2010.

In September 2010, Russia’s then-president Dmitry Medvedev signed a decree on measures to implement the UN Security Council’s Resolution 1929 of June 2010 to prohibit the supplies of S-300 to Iran. The contract was annulled and the advance payment returned to Iran.