Why invading Iran is not the only option

Mahmoud Ahmadinejad's 7 month tenure in Iran has been an interesting period of interenational politics. He has made a number of bold gestures: 1. His holocaust denial 2. His assertion that he wishes to 'wipe [Israel] off the map' 3. His stubborn and bold resumption to Iran's nuclear programme. All have been bold high profile statements of international intent.

However, he has had what would be considered by most standards an absolutely disastrous introduction at a domestic level. His mandate was provided by the considerable Iranian poor. His 'back to basics' fundamentalist approach appealed to an electorate who wanted strong domestic leadership. However, in office his promises are proving difficult to implement as Tehran's more moderate business class are proving a difficult block to his domestic reforms. Unlike Afghanistan where the Taleban held power or even Hamas who have gained power (or what passes for power) on a fundamentalist standpoint, Iran has real economic clout and the middle class Iranians hold that power in Iran. What he's finding domestically therefore is that he is having to appease the middle classes which fundamentally goes against what he stood for in the election and the poor section of the country is becoming restless as to why nothing's happening.

Add to that, that he has had 3 nominations rejected in parliament for Iran's OPEC representataives and he has lost the confidence of the Supreme Religious Leader Ayatollah Ali Khamenei who is leaning increasingly towards the defeated conservative pragmatist and more moderate Akbar Hashemi-Rafsanjani.

Which brings me on to my point. Why are Western powers posturing and threatening sanctions and invasion (we are being softened up in the same way we were before iraq) when there is a much simpler option? An option that is not politically laudable, but nevertheless avoids the inevitable tensions that even the threat of invasion will garner. It's millenniums old but seems to be being overlooked. Yes it's good old regime destabilisation. With a domestic position that is tenuous to say the least, it is by no means beyond us to support Rafsanjani and to support the will of an increasingly strenghthened Iranian middle class. The big issue that faces us at the moment is Khameni's hardline position on the cartoons, it's a posiion that will sit well with the poor and creates a strong alliance again with Ahmadinejad.

Sanctions or war are not the only way, I simply don't understand this show of strength that seems the default position of the US and the UK.