Leading article: A show of force as the Islamic revolution fights back

Iran's belligerence reflects weakness, but it is no less dangerous for that

When it became known that Iran's Supreme Leader, Ayatollah Ali Khamenei, was to address Friday Prayers at Tehran University, there was a sense of anticipation that went far beyond the city bounds.

Having initially endorsed the official election victory of Mahmoud Ahmadinejad and then sanctioned a partial recount, the ayatollah had seemed to give ground. His decision to speak yesterday in one of the hotbeds of support for the main opposition candidate, Mirhossein Mousavi, raised hopes that further concessions might be in the offing.

How quickly, and comprehensively, were those hopes dashed! The ayatollah delivered a long and at times overtly menacing address, in which he conjured up once again the old image of the enemy: the UK, Israel and the United States. Television pictures of rows and rows of young men, waving their fists and shouting threats, hardly sent a friendly message to the Western world; Britain was singled out for "treachery".

The message, of course, was not primarily for outsiders; it was for Iranians. Stressing a non-existent but not implausible, outside threat is after all the most tried and tested method of fostering internal unity. But to understand this does not make what Ayatollah Khamenei had to say any more consoling. If Iran's theocracy had ever wavered about its response to the opposition street protests – the most acute challenge it has faced since the Islamic revolution – it now appears to be in full retrenchment mode.

The ayatollah used the weight of his office and the sanctity of the occasion to demand an immediate end to the street protests, rule out any possibility of vote-rigging, and – in a clear reference to Mr Mousavi and his supporters – threaten that political leaders would be held responsible for any violence. It does not automatically follow from this that the authorities will now crack down on the demonstrators with the force that they have at times threatened (though, thankfully, not yet used). But it does suggest that the days of open protest could be numbered. It also discredits any lingering expectations that the recount, such as it is, will be worth anything.

There was already abundant evidence of retrenchment – in the efforts of the authorities to block access to the internet, curb mobile phone traffic and restrict the activities of foreign reporters. Amnesty International has reported that almost 200 people have been detained, including former ministers and leading reformists. But Friday Prayers showed conclusively which way the wind was blowing. Whatever the rights and wrongs of the election, these are not the actions of a confident regime. Nor does it bode well for what is to come.

The most benign interpretation of Ayatollah Khamenei's address is as a show of force designed to strengthen the regime's hand in advance of his meeting today with Mr Mousavi and other opposition candidates. The likelihood of the new election they want already looks small to vanishing.

But a longer-term intention cannot be ruled out: to suppress, rather than accommodate, the opposition. And if this proves difficult – as it will, so long as memories of the tumultuous past week remain alive – the regime will behave defensively, as all weak regimes do. It will resist calls to ease up at home – for instance, by enhancing rights for women – and it will ignore, even reject, President Obama's outstretched hand. Iran and its immediate neighbourhood have just become a more dangerous place.