While American policymakers are fond of repeating the mantra that "all options are on the table" when it comes to dealing with Iran and its nuclear program, the president publicly took one option off the table during his recent visit to Israel: Speaking to college students, Barack Obama reiterated, "Iran must not get a nuclear weapon. This is not a danger that can be contained."
If the Obama administration has indeed definitively rejected containment as an option, the United States will not develop contingencies for if and when Iran crosses the nuclear threshold. That means Washington is now committed to preventing Iran not only from acquiring any sort of deployable nuclear capability, but also, implicitly, from reaching the breakout stage where Tehran would possess the necessary capabilities to quickly assemble a bomb. This puts Washington further away from the Russian position, for instance, which is in full agreement that Iran should not possess a nuclear weapon but is far more agnostic on whether Iran can be trusted with the technological building blocks from which a weapon might be fabricated. The United States, in contrast, is not willing to take the risk of Iran even having the tools to construct any sort of nuclear device.
Whereas containment might entail a policy of stringent monitoring to prevent Iran from building an actual weapon, under the position Obama staked out in Israel, the United States is committed to the dismantling of Iran's nuclear efforts back to the point from which it would be impossible to create weapons. Most prominently, this means rolling back Iran's domestic uranium enrichment capabilities, but related issues, such as Iran's development of ballistic missiles, also remain sticking points in the negotiations between Iran and the West.