

If Iran ultimately goes nuclear, the U.S. might have to move some of its own nuclear weapons into the Middle East to keep Tehran contained and deterred, according to the Pentagon's recently departed chief of Mideast policy.

Colin Kahl, who left the Pentagon in December, argues in Foreign Affairs that bombing Iran should be a "last resort." He wants to give sanctions and diplomacy time to convince Iran that a nuclear weapon isn't worth the costs. If that doesn't work, then the U.S. might need to consider drastic steps to keep Iran boxed in.

Because while Kahl thinks that all the troops and gear parked near Iran – including at least two aircraft carrier battle groups, Patriot missile batteries across the Gulf, and Aegis ballistic missile defense ships – should be sufficient to deter Iran, perhaps they should be "supplemented by a limited forward deployment of nuclear weapons and additional ballistic missile defense." If so, that could mean that a miscalculation between the U.S. and Iran could escalate into a nuclear exchange.

Kahl insists that he's not endorsing stockpiling U.S. nukes in the Gulf. "I was alluding to a broader theoretical debate about the possible requirements for extended deterrence," he tells Danger Room, "but not advocating that we necessarily go down this road."

By "extended deterrence," Kahl's referring to an idea that has vexed nuclear strategists since the Soviets got the bomb. How do you make sure your adversary knows you mean business? Both Obama and President George W. Bush pledged not to accept a nuclear Iran. But if Iran goes nuclear and there isn't an attack – which Kahl, like many others, writes could have unacceptably disastrous consequences – then Iran might not consider American deterrence credible.

Hence, perhaps, the nukes. That could go any number of ways: permanently stationing tactical nukes in the Gulf, a la Cold War Europe; sailing nuclear-armed submarines through the region occasionally; or deploying "dual-purpose" bombers – planes that can drop either nuclear or conventional bombs.

But Kahl emphasizes that he's not airing an idea Obama is secretly considering. "This doesn't represent any internal dialogue by the administration," he says. "The president is focused on prevention, not deterrence." In recent days, for instance, Kahl's old boss, Secretary Leon Panetta, has stated that a nuclear Iran would be a "red line" for Washington.

But it does speak to how dangerous the region could get if Iran goes nuclear. It might be preferable to bombing. But deterring a nuclear Iran will also be hard – especially if the U.S. moves its own nukes into the world's most volatile region.

Photo: National Nuclear Security Administration