Reports are swirling that Russia is finally delivering an advanced S-300 air defense system to Iran, although they may be premature again.  The implications of that and the other items on Iran’s military shopping list need our attention fast.

An Iranian military hardware spree can quickly fuel a Middle East arms race, drive U.S. allies to seek more advanced weapons, and, in the case of Israel, spur development of their own. 

More importantly it can force the West to change the way it thinks about possible military confrontation with Iran and even about how it can operate—if at all-- in the Persian Gulf.

The S-300 PMU-2 mobile surface-to-air system, with four launchers per battery, is just one example. It can identify and shoot down aircraft 120 miles away. Its mobility makes it hard to find and destroy, and the Mach Seven speed and accuracy of its missiles makes them deadly.  The S-300 will mark the first upgrade of Iran’s missile defense system in nearly 40 years.

But Iran wants much more. The Minister of Defense and Armed Forces Logistics, Hossein Dehghan, presented Moscow with a $6 billion shopping list in February, including the Yakhont anti-shipping missile, the Su-30 long-range air superiority fighter-bomber, T-90 tanks, and other goodies.

Ali Akbar Velayati, a close advisor to Iran’s Supreme Leader, has declared that Vladimir Putin’s regime “wants to positively respond to such requests.”  

The Yakhont is a supersonic missile that can hit ships with great accuracy out to 180 miles or so. Experts are convinced that Russia has already placed the Yakhont in Syria.

Yakhont missiles on the Iranian coast would threaten all shipping– merchant and military-- in the Persian Gulf.  They could force the U.S. Navy and its partners to reconsider whether to deploy aircraft carriers or big-deck Marine amphibious ships in those waters—a huge rebalancing of U.S. forces and diplomatic leverage.

The Su-30 that Iran has also requested is roughly equivalent to the F-15E Strike Eagle. Its delivery would be the first upgrade to Iran’s air capabilities in decades.

With a combat range of about 750 miles (roughly equivalent to the Shahab 3 intermediate-range ballistic missile), the Su-30 could give Iran  rough parity with its Arab-speaking Gulf Cooperation Council  rivals and even with U.S. and allied aircraft in the region.

Iran would suddenly have a vastly improved air defense and an impressive degree of sea control throughout the Gulf, in the Strait of Hormuz, and well into the North Arabian Sea.

All of this would come alongside a growing array of Iranian ballistic missiles that are being tested in total disregard for the United Nations Security Council Resolution that forbids them.

The Yakhont and Su-30 purchases are far from done deals.  The Su-30, in particular, falls  explicitly under the same U.N. Security Council resolution that endorsed the nuclear agreement. 

For what it’s worth, that resolution gives the U.S. or any permanent member of the Security Council the power to veto such a weapons delivery, and the Obama Administration has said that it will use that power. 

The Iranians don’t seem worried. They recently reiterated their conviction that a Su-30 deal will be completed this year. 

Their optimism is not groundless. The U.N. Security Council resolution does not impose automatic penalties on either Iran or Russia for violating the weapons ban and completing the transaction, either while bypassing the Security Council or despite a veto. 

The sale would not violate the nuclear deal itself and thus could not be used to invoke much-touted “snapback” sanctions. 

The U.S. would thus be forced to forge a new coalition to impose sanctions or take other actions against Russia and/or Iran—or else helplessly watch the deal go through.

The military balance in the Middle East is at stake in these considerations. 

It is not enough for the administration to promise to veto the sale of these systems, although that is essential. 

It must start right now to build an international coalition to impose penalties on Russia and Iran in the event of any deal, and it must be prepared to impose unilateral sanctions on Russian and Iranian individuals and companies flouting the weapons ban imposed by the Security Council. 

Words and votes alone are not enough to meet this challenge. Iran is muscling up, and we should be prepared for it.

Vice Admiral John Miller (USN, Ret.) was most recently commander of U.S. Fifth Fleet in and around the Persian Gulf.

Frederick W. Kagan is the Christopher DeMuth Scholar and the director of the Critical Threats Project at the American Enterprise Institute.