I doubt they could actually do it. Any attempt to do so would result in the prompt destruction of their limited navy. However, it does accomplish two things:
It sends the price of oil higher with escalated tensions in the region. Also, it exposes our dependence on foreign suppliers (even if the major contributors are neighbors). We need an energy policy to take this potential weapon away from those who may wield it.
Hey didn’ t I just read that our navy has a great new supply line of $15/ gal biofuel? What cheap oil we don’ t need no stinking cheap oil....
They can easily close it with their C-802 varian cruise missile.
Here is my take for what it is worth:
Iran has cornered themselves. They are too far in to stop (convincingly) with nuclear weapon development. They are being attacked covertly and politically (finally with some effect). The explosions, the UAV, the scientists killed, etc. A real world leader would be adding force multipliers to the stress Iran is feeling from the world. I think they expect an attack but are pretty twitchy about when and where it will come. A good counter strategy is to instigate an attack in the right spot to get your oponent to show their hand and a reason to retaliate offensively.
The greatest political problem is Israel’s involvement in a war with Iran (or at least that is what Iran thinks). Israel brings some tools to the table that would be useful. Iran is looking for an excuse to start firing on Iran from Syria, Iran and anywhere else they can get shells on target from. Their hope is to completely destabilize the region and have Egypt, Jordan, Syria, Pakistan, etc involved. The most important strategy is not the military any of those countries bring to conflict. It is the side they take and the instability it creates in all ME nations.
Iran is hoping for a catalyst that doesn’t point blame at them (IMO). They hope to garner Muslim sympathy in the region (at least with the people) and have an excuse to go on overt offense.
American forces sinking a ship or two in the Straight would do just fine for them. Problem is, I doubt we would actually do anything about it. We would probably lead from behind.