Iran has a very powerful weapon in its threats or ability to close the Strait of Hormuz however I think it is a double edged sword.
Iran is a net exporter of oil so closing the strait would reduce its ability to earn export income. It is also a net importer of fuel as it only has enough capacity to refine about 50% of its domestic requirements so a closure would also affect its ability to import this. Other Middle East oil producers might also get a bit annoyed with Iran and therefore cut off their exports to the country. Either way this would lead to domestic supplies would be squeezed and the population would be effected.