Russia and Iran seem intent on crashing President Barack Obama’s honeymoon. Last month the deputy chairman of the Iranian Parliament’s Commission on National Security and Foreign Policy told Iran’s official Islamic Republic News Agency that Russia had agreed to deliver S-300 missile components to Iran. Heritage Senior Research Fellow Ariel Cohen breaks down the impact:

Allegations that Russia may be supplying Iran with S-300 missiles have circulated in the media since 2005. Such missiles could boost Iran’s defensive capabilities against possible airstrikes targeting its nuclear program. In the past, Moscow denied Iran’s statements that such deliveries had taken place.

The latest row over S-300 sales came after Iran’s official Islamic Republic News Agency cited a senior Iranian MP, Ismail Kosari, as saying that Russian and Iran had finalized the S-300 deal and Russia had started supplying the systems. This was predicted last fall in Washington by a visiting Russian official with good knowledge of the region. While Iran has neither confirmed nor denied the statement, military experts do not rule out the possibility of on-site S-300 assembly from components allegedly supplied to Iran.

Although the sale of the S-300 to Iran is not prohibited, such a deal would be a game-changer in the Middle East. First, with S-300’s range of close to 200 kilometers (120 miles), Tehran could threaten U.S. and allied troops deployed in Afghanistan and Iraq, if it were to deploy the system along Iran’s borders. Second, it would boost the defense of Iran’s Bushehr reactor, which Russia has built. Finally, Tehran also could use S-300s to protect its Natanz uranium-enrichment plant.

Iran’s current air defense system is outdated and would not defend against a massive airstrike aimed at its nuclear facilities. Israel, or under certain circumstances, even the United States, does not rule out the possibility of such a strike. If S-300s enter into service in Iran, they may deter potential strikes by Israel, unless Israel either acquires new American F-35s capable of destroying S-300s or executes a pre-emptive strike on Iranian S-300s before they become fully operational.

It’s all a question of timing and capabilities. Experts estimate it may take up to one year after delivery for Iran to install S-300s and make them operational. The F-35s will be available to Israel no earlier than in 2011-2013, according to defense industry estimates. The sand in the Middle Eastern doomsday scenario clock is running out.