Obama must be ready to use force against Iran to end nuclear standoff Yet the risks of a nuclear armed Iran are far greater. Were Iran to gain nuclear weapons, its violent revolutionary project would go radioactive. Today's political situations in Lebanon and Iraq attest to what this would mean. Because in Beirut, Baghdad and beyond, Iran uses a toxic mix of violence and brutal political blackmail to advance its sectarian agenda: the expansion of Khomeini's "jurist guardianship" ideology. With nuclear weapons, however, Iran's hardliners would have the security umbrella to redouble these efforts. In basic terms, that would mean increased terrorism and a greatly destabilising arms race across the Middle East. After all, made paranoid by Iran's Shia expansionism, the Sunni Arab monarchies would almost certainly pursue their own nuclear weapons. Middle Eastern political instability would thus find thermonuclear expression. And an emboldened nuclear Iran would also pose a greatly increased threat to the west. Consider that in 2011, in an action approved by senior officials, Iran tried to blow up a Washington DC restaurant. In short, a nuclear armed Iran must be prevented. And if Mr Obama escalates his military threats, it can be. While Iran's hardliners are bold, they're also realistic. Take Qassem Suleimani, Revolutionary Guards commander of Iran's covert-action Quds Force. At present, Suleimani is pictured nearly every day in Iraq, where he's leading Iran's action against the Islamic State. He's also responsible for many attacks on US and British forces in Iraq. In every sense, he's a hardliner. But he's also alert to the reality of US military power. And that reflects an underlying truth. Where Isil are frothing thugs, Iran's rulers are masters of calculation, making strategy in view of the opportunities and risks of each moment. If Mr Obama is willing to increase his pressure on the hardliners, they will be deterred. In that regard, President Obama should immediately deploy two more carrier strike groups to the Arabian Sea. Joining the current on-station group, the USS Carl Vinson, these forces would establish a US air dominance capability joined to robust fleet protection. At present, the US only has two carrier groups deployed globally. This broadcasts absent resolve. Complementing the new deployments, President Obama should also express his impatience with Iran's diplomatic games. Abandoning his previous equivocation, in explicit language, Obama should state that he'll use force against Iran's nuclear program if a deal isn't reached. Finally, Obama should explain that if Iran responds to any US action with major retaliation, he will respond with overwhelming force against Iranian military forces in the Persian Gulf and regime targets in Tehran. This is crucial; at the moment, Iran's leaders think they've deterred the military option. Witnessing Mr Obama's change of tone and its physical substance, Iran's hardliners would quickly take notice. Coupled to continued economic sanctions and Iran's reduced government revenue from lower oil prices, Obama's tangible threats would challenge Iran to reconsider its strategic calculations. To be sure, serious diplomacy offers by far the best solution to this crisis. I supported last November's six month negotiating window and I concede that any deal with have to allow Iran a low-enrichment baseline. Nevertheless, Khamenei must learn that he doesn't hold the cards. For the cause of peace, Iran must find renewed contemplation of American military power.