Russia and Iran on Monday have signed a deal for Moscow to begin delivering S-300 surface-to-air missile systems to Tehran, said Sergei Chemezov, the chief executive of Russia's state technologies corporation Rostec, quoted by the RIA news agency.
"The contract between Russia and Iran for delivery of S-300 missile systems is back in force," Rostec said in a statement, adding that the two sides had "signed a contract".
Both Russia and Iran had signed a $800 million deal to receive five S-300 missile systems in 2007 however, the delivery was cancelled in 2010, when the United Nations (UN) imposed sanctions on Iran over its much debated nuclear programme.
In 2011, Iran filed a lawsuit against Russia for suspending the contract, seeking billions of dollars in damages in return.
Russian President Vladimir Putin lifted the ban in April 2015, after Iran and the P5+ 1 countries, consisting of the US, Britain, France, Russia, China and Germany agreed on a nuclear deal.
As part of the deal, Iran agreed to curb its nuclear programme in exchange for the removal of UN sanctions and arms embargo over the country.
The agreement of the nuclear program, however, has not pleased Saudi Arabia and its Gulf allies as they believe the nuclear deal might give some privileges to Iran in order to unlock its geopolitical and geoeconomic isolation in the region particularly after the conflicts erupted in Iraq, Syria and Yemen.
Iran is known for its solid support to Syrian president Bashar al Assad and its backing of the Syrian military, through sending weaponry and human resources.
However, Chemezov has stated that Gulf countries had no reason to feel threatened by the deal.
"This is defense equipment. And we are ready to offer this defense equipment to any country," Chemezov later told Reuters in Dubai, speaking through interpreters.
"So if the Gulf countries are not going to attack Iran ... why should they be threatened? Because this is defense equipment."
"Five years ago ...up to now ...we said that the S-300 is not capable to attack ... to reach the neighboring countries," Chemezov added.