Russia has already delivered half of S-300 air defense systems to Iran under the existing contract, Russian Deputy Prime Minister Dmitry Rogozin told reporters following russia-Iran-Azerbaijan summit in Baku on Monday.

Head of Russia's Rostec corporation, Sergei Chemezov, said in July that Russia was planning to complete the deliveries of the S-300 air defense systems to Iran by the end of 2016.

The $800-million Moscow-Tehran contract to deliver Russian S-300 systems to Iran was signed in 2007. It was suspended after the adoption of UN Security Council sanctions on Iran in mid-2010.

In 2011, Iran sued Russia in the Geneva Arbitration Court after Moscow suspended the contract in 2010, citing a UN Security Council resolution that placed an arms embargo on Tehran.

Russian President Vladimir Putin lifted the S-300 delivery ban in April 2015, shortly after the P5+1 group of international negotiators and Iran reached a framework nuclear agreement to remove all economic sanctions against Tehran in exchange for its pledge to ensure that all nuclear research in the country will be for peaceful purposes.