The S-300 anti-aircraft missile system at the Victory Parade, Red Square, 2009. Photo: Wikipedia.

Russia’s widely-reported sale of advanced S-300 missile defense systems to Iran is “far from a foregone conclusion,” said a recent analysis from U.S. think tank the Washington Institute for Near East Policy.

Conflicting reports have emerged over the last several weeks over whether the deal, originally inked in 2007, was set to go through, with Iranian officials largely claiming it is while others in Moscow contend that the deal is still being held up.

“Russia’s latest bid to resurrect negotiations over the missile system may simply be another attempt to use threatened arms transfers to achieve other goals,” wrote researchers Michael Eisenstadt, director of the Military and Security Studies Program at the institute, and Brenda Shaffer, an adjunct professor at the Center for Eurasian, Russian, and East European Studies at Georgetown University.

Specifically, the scholars said Russia could use an ever-pending S-300 deal with Iran as leverage over the U.S. and Europe for concessions regarding the conflict in Ukraine, where thousands have been killed in the armed insurgency in the country’s east.

But the deal could be snagging because of technical issues as well. Russia is in the process of updating one of its S-300 systems, and if Iran decides to go for another, the Antey-2500, it would have to wait behind Egypt, which recently purchased the system.

Russia recently invited the leaders from several Sunni Arab states to discuss arms deals in the wake of the nuclear deal with Iran, which has left many of these countries outspokenly uneasy about a bolstered regime in Tehran.

“Ironically, the continued delays may suit Russia just fine. Moscow views Iran with a mixture of deep distrust (due in large part to its ability to threaten Russian interests in the Caucasus and Central Asia) and exasperation (due to the difficulty of previous S-300 negotiations),” the authors wrote.

Russia is also likely using the arms deal to pressure Iran to drop a $4 billion lawsuit against Russian weapons firm Rosoboronexport over the initial unfulfilled S-300 contract from 2007.

Iran’s desire to complete the deal with Moscow and get the S-300s operational is clear, the authors contend: Iran has a spotty and outdated air-defense system, and installing the mobile batteries could further deter foreign armies, most notably the U.S.’s and Israel, from launching air strikes against Iran’s contested nuclear sites. Other analysts have noted that Iran could use the S-300 system to harass non-hostile aircraft in neighboring countries, should conflicts arise.