“[The presidential] decree lifts the ban on transit through Russian territory, including airlift, and the export from the Russian Federation to the Islamic Republic of Iran, and also the transfer to the Islamic Republic of Iran outside the territory of the Russian Federation, both by sea and by air, of air defense missile systems S-300,” says the information note accompanying the document, RIA Novosti reported.

The decree enters into force upon the president’s signature.

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The contract for supplying S-300 missile systems to Iran was signed in 2007 and implied the delivery of five S-300 squadrons worth $800 million. But in 2010 the contract was put on hold due to the UN imposing sanctions on Iran.

Tehran answered with filing a nearly $4 billion lawsuit against Russia’s Rosoboronexport arms dealer company to a Geneva arbitration tribunal.

The question of S-300 supply to Tehran remained unsettled for years.

After years of negotiation, in February 2015, Moscow offered Tehran the chance to buy its latest Antey-2500 anti-aircraft and ballistic missile system, instead of the older S-300 system. Iran replied that it would consider the offer.

The last time Russia supplied S-300 systems abroad was in 2010, when 15 squadrons were delivered to China.

Since then production of S-300 systems has been suspended as the main producer of the Russian air defenses, concern Almaz-Antey, has launched production of the next generation systems, S-400. China has become the first country allowed to buy S-400 systems, Rosoboronexport chief Anatoly Isaykin told the Russian media.

As of today, S-300 systems have been operable in a number of countries, including Algeria, Azerbaijan, Belarus, Cyprus, Kazakhstan and Vietnam. There is a valid contract to deliver S-300 systems to Syria, but it was put on hold after the beginning of the civil war in the country.