Quite agree that Iran's primary goal is become the regional hegemon and to pursue continued expansion of the Iranian clerical vision of Islam. To that end, the tactic of baiting and taunting of Israel and the US and holding up the results of that baiting to the rest of the Muslim world in general and the ME in particular have proven quite succesful for them for many years now. No reason they should cease using a proven tactic now. A key part of that baiting is the continued issuance of inflammatory statements of the sort for which Khomeini and now Ahmadinejad have become (in)famous, i.e., the "one nuke eliminates Israel, but several nukes later and we're still here" type of thing.
A major risk when applying this train of thought to Iran is first, the Iranian government is effectively controlled by clerics, and second, the religion of the controlling clerics is quite violent in many aspects. The Quran is quite explicit in its exhortations to either convert or kill non-Muslims. Just how fundamental are the clerics who make up Irans ruling council? Do they embrace all aspects of the Quran, including the exhortations to either convert or kill non-Muslims? Or are they of a more moderate persuasion?
Their public statements with respect to Israel and the US are certainly designed for Muslim consumption, but how much further should the rest of the world take them? Iranian actions (e.g., their support of terrorism via proxies, their demonstrated pursuit of nukes) suggest that we should not take their words lightly. Dare we stop short of ruling out their use of nukes, either directly or via a proxy?
Whether Christian or Muslim, there is no fanatic as convinced of the rightness of his cause and his actions in furtherance of that cause, as a religious fanatic.