MEMRI reports that The Iranian government has recently reiterated their intention to shut down the Strait of Hormuz if they are attacked:

...in the event of military action against Iran by the enemies [i.e. the U.S. and Israel], the geostrategic role of the Persian Gulf, and especially of the Strait of Hormuz, will come into play as part of Iran's defense [plan, as well of its policy] of harming the interests of both the attackers and their supporters. The policy of closing the Strait of Hormuz was drawn up [expressly for this purpose]; it is made possible both by the Strait's geographic location and by the IRGC naval forces' capabilities in the Persian Gulf ... "In the event of [military] action by an enemy, no one should expect Iran to refrain from using every [available] means of self-defense, including closing the Strait of Hormuz with a view to damaging the invaders' interests. Closing the Strait of Hormuz is part of Iran's defense policy in face of the U.S. military threat..."

The Iranian policy is based on an accurate, if not obvious, recognition of the importance of oil in the global economy and thus the Strait's unique strategic importance:

"The Strait of Hormuz is one of 14 locations in the world with unique strategic importance. Over 60 percent of the world's energy reserves are located in the Persian Gulf, and 17 million barrels of oil are transported daily from the strait by oil tankers. In today's global economy, oil plays the same role as blood in the human body, and under present circumstances, it is impossible to conceive of an active and dynamic economy without oil. Industry is completely dependent on [Persian] Gulf oil for survival.

What the Iranians are not saying- and understandably so- is how they plan to keep their own economy afloat or how they plan to get their own oil and gas to world markets or even how they will keep the lights on in Teheran and Qom if and when they undertake a game that more than one can play.