If push comes to shove, Iranians will unite to defeat an external threat

In the face of an outside threat, the two factions can be expected to join forces in a common religious and nationalist cause.

The regime's cadres are infinitely better equipped, trained and motivated than Hussein's, and the regime is also well positioned to draw on many ordinary Iranians' devotion to Islam and sense of historical nationalist pride to mobilise massive resistance to an outside attack.

In the event of a conflict, the only forces on which the US could count would be dormant secularists and disillusioned Islamists. But these forces are too small and disorganised to provide the kind of leadership that the Islamists did in ousting the Shah.

Under greater US-led international pressure, the regime is likely to respond in one of two ways. The first is to allow its reformist faction to have a wider exposure in both domestic and foreign policy arenas, provided that it is persuaded that the US policy towards Iran is not one of regime change.

Another is to move down the same path as North Korea: to achieve a nuclear capability as the best means of deterrence to ensure its survival. If the US and its allies are not careful, the latter option may gain potency.