The contract to deliver five 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 April 2015, Russia resumed the talks on the S-300 deliveries following an interim agreement on the Iranian nuclear program.
In December 2016, Iran's ambassador in Moscow Mehdi Sanayee said that Russia had finished executing the contract on supplying Iran with divisions of S-300 missile systems to Iran. Tehran purchased S-300 missile systems from Moscow. According to media reports, Russian-made S-300 air defense systems delivered to Iran will become operational by late March 2017.