Sanctions have proved ineffective time and again and are not likely to obtain a different outcome in the case of Iran. Faced with shortages and economic privations, the Iranian populace will blame the West and cluster more closely around the current regime.
Sanctions are also unlikely because they would cut off Iranian oil. China would never tolerate this because of its dependency on Iranian oil, and the US economy could not bear the increase in the cost of oil. Iraq also taught us that sanctions could also serve as a fertile breeding ground for corruption and allow the government further leverage in exercising its power. Also, the US cannot leverage Iranian access to America's vast economy because it has already been closed to Iran for 27 years.
Military strikes would be a godsend for the regime in Iran, especially the hardliners that the United States most fears. Targeted strikes on several key installations might indeed disrupt the nuclear program, but again these would generate immense consequences for the US and its allies. Military strikes would create ill-will from ordinary Iranians and extend indefinitely the lifetime of the regime. Such strikes also would not be enough to topple the regime and no government now has the manpower or will for such an occupation.
To the degree that military strikes would be successful and would manage to destabilize the regime, US foreign policy would be faced with a vortex of anarchy stretching from Islamabad to Damascus. The internal chaos in Iran in the early 1980s showed how deep and virulent Iran's ideological divisions can be. All of these divisions could be strengthened or influenced by elements outside of Iran were the regime to collapse. This, coupled with the potential for ethnic unrest from the almost 50% of Iran that is not Persian, could lead the country into a long civil war. Furthermore, even if a stable regime were to emerge, there is no guarantee that it would be a more responsible international citizen.
http://www.atimes.com/atimes/Middle_East/HC18Ak04.htmlin other words : you hated Iraq ? you ain't seen Iran yet...