Leading article: A complex and uncertain contest for Iran's future

Iran is experiencing its most tumultuous days since the 1979 revolution. Faced with vast street demonstrations by those incensed by the declared result of last week's presidential elections, the ruling regime in Tehran is being pulled in opposing directions. The Guardian Council yesterday announced that it is going to recount disputed votes; an extraordinary attempt to address the concerns of protesters. But at the same time strict controls have been placed on the movement of foreign journalists and dozens of prominent opposition figures have been detained.

It is impossible to say with any certainty what the outcome of this struggle will be; whether those sympathetic to the complaints of the demonstrators will prevail over the security hardliners. We should certainly not underestimate the disruptive potential of these demonstrations. Iran's students played a crucial role in bringing down the Shah in 1979. And like their forebears, educated young people in the country today are in full cry, aided this time by the organisational power of modern telecommunications. If the protests, which have primarily been in Tehran, spread around the country, the momentum they generate could prove unstoppable. Some even suggest that the scale of the protests and the hesitancy of the authorities' response have placed a question mark over the very survival of the regime.

Yet there are strong reasons for caution. Widespread protests by student reformers in 1999, 2003 and 2008 were successfully suppressed. And the present regime enjoys far more legitimacy than the Shah ever did. Nor should we assume that the opposition are correct when they claim that President Ahmadinejad has stolen the election. The results announced on Saturday certainly give grounds for suspicion, especially the fact that the leading opposition candidate, Mir Hossein Mousavi, appears to have done so badly in what was expected to be his heartland. But President Ahmadinejad has always enjoyed considerable popular support, particularly among Iran's poorer, rural voters. It is possible that a recount will show that he did indeed win the poll, even if by a smaller margin than originally declared.

There is another factor which those talking up the idea of a new revolution in Iran need to remember. Mr Mousavi has an outspoken and liberal wife but the candidate himself is no anti-regime firebrand, having served as a conservative prime minister through the Iran-Iraq war. He is also closely associated with the regime's veteran power-broker, Ali-Akbar Hashemi Rafsanjani. What we are witnessing is as much a struggle within the Islamic regime as an assault on its rulers from outside. Indeed, it is possible that the regime will ensure its survival by doing a deal which reduces President Ahmadinejad's powers and hands a prominent role to Mr Mousavi somewhere else in the regime's labyrinthine power structure.

There is a final reason for caution for those anticipating a fresh start in diplomatic relations. Despite the crude characterisation of the Islamic republic as a repressive autocracy in the Western imagination, its policies have always, to a certain degree, rested on the foundation of popular consent. That means that even if the regime falls, the policies of the government that emerges from the rubble might not be substantially different from those of its predecessor.

So how should the outside world respond to what is taking place in Iran given these considerable complexities and uncertainties? The Obama Administration has acted sensibly so far, expressing concern about the reports of violence and the allegations of vote-rigging but refusing to voice support for the demonstrators. That was the mistake the Bush Administration made in 2003 when the former president praised the student protests as "the beginning of people expressing themselves toward a free Iran". That intervention ended up rallying domestic support for the hardliners and undermined the very reformists the US was trying to support.

Iran's nuclear programme, its sponsorship of Palestinian militants, its oil exports and its control of the world's most strategically important shipping lane make the country the hinge of global diplomacy. The extraordinary events of recent days will sorely tempt Iran's neighbours and other powers to try to tip the scales in favour of their preferred outcome. But that is an urge that must be resisted. Now is the very worst time for the world to attempt to exert any influence in Iran.

There is a Persian proverb that says: "He who wants a rose must respect the thorn". Unless the outside world desires to get pricked, it will, for now, take a step back from this domestic struggle for Iran's future.