Russian President Dmitry Medvedev issued a decree Wednesday banning all sales of S-300 anti-aircraft missile systems to Iran. Russia signed a 2007 contract to sell the sophisticated systems that could boost Iran's ability to defend against air strikes. Israel and the United States have objected to the deal, and no such missiles have been delivered yet. Medvedev's decree also prohibited exports of tanks, aircraft and sea vessels to Iran.
This was not unexpected. If anything it comes as a relief of sorts to the Iranians, as the matter is no longer subject to open-ended limbo. The Iranians will likely receive their money back, possibly with a penalty sum attached for nondelivery. Meanwhile, continued development of an Iranian equivilant, the IR-300, is on-going according to Iranian defense officials.