Iran and Russia have been in negotiations over the transfer of an advanced missile system to Iran (http://www.bloomberg.com/news/articles/2015-06-02/russia-may-start-s-300-deliveries-to-iran-by-early-2016 ; http://www.businessinsider.com/why-russian-s-300-sale-to-iran-is-a-big-deal-2015-6 ; http://www.ibtimes.com/russian-s-300-missile-sale-iran-will-go-ahead-despite-us-nuclear-deal-2020762 ).