Now Iran knows that Washington means business

These are undoubtedly challenging times for Iran’s ruling regime. First there was the attack on a military parade in the south western city of Ahvaz, the worst terrorist incident to take place in Iran for nearly a decade.

This was quickly followed by US president Donald Trump using his appearance this week at the United Nations General Assembly to make yet another uncompromising attack on Iran's conduct, denouncing the regime as a "leading sponsor of terrorism", having a malign influence on the region and lying about the true extent of its nuclear activities.

Being subjected to harsh criticism from an American president is hardly a new experience for the ayatollahs. American presidents from Jimmy Carter onwards − with the notable exception of Barack Obama − have often taken a hard line with Tehran, culminating with the administration of George W Bush designating Iran as part of an “axis of evil”, together with Iraq and North Korea.

Iraq was removed from the list following the overthrow of Saddam Hussein in 2003, and North Korea also appears to be heading for the exit, following the extraordinary summit between Mr Trump and North Korean dictator Kim Jong-un in Singapore in the summer.

But Iran, despite all the efforts of the world’s leading powers to establish a more constructive relationship with Tehran, remains resolutely in the rogue nation category − at least as far as the White House is concerned. The ayatollahs’ usual response, when faced with such trenchant criticism, is simply to ignore it, or to claim it is all part of an American-led conspiracy to overthrow the Islamic revolution.

That was certainly how Iranian president Hassan Rouhani reacted when his turn came to address the UN, when he accused Washington of indulging in "economic terrorism" through its decision to reimpose economic sanctions.

But while the regime’s natural instinct will be to tough out this latest deterioration in relations between Tehran and Washington, the Iranian leadership will also be well aware that, this time, Washington means business, and that the regime could soon be facing its most severe challenge since the 1979 revolution.

For a start, the Ahvaz attack has come amid nine months of broader, nationwide anti-government protests. The primary focus of the protests has been the dire state of the Iranian economy, particularly since the precipitous collapse in the value of the rial. But the demonstrators have also vented their anger at the government's preference for spending vast sums on its overseas military adventures, rather than investing in the economic well-being of its own citizens.

Moreover, the economic pressures on the regime are likely to increase further as the US ramps up the sanctions regime against Iran, while at the same time putting pressure on its European allies by threatening to take measures against those who continue to do business Tehran.

But it is, arguably, Iran’s continued meddling in the affairs of neighbouring Arab states where the ayatollahs are at their most vulnerable, as the Trump administration seeks to contain the disruptive activities of the Revolutionary Guard Corps.

The national security team now advising Mr Trump is arguably the most hawkish of the modern era. Moreover, the likes of Defence Secretary James Mattis and Secretary of State Mike Pompeo have first-hand experience of dealing with Iran in their previous careers in the military and the CIA respectively, while National Security Director John Bolton has devoted most of his career as a leading light in the neoconservative movement to denouncing Iran.

And, apart from holding Iran to account over its nuclear programme, their clear priority is to prevent Iran from building further on the extensive military network it has established around the Middle East in recent years. As one senior security official in Washington told me recently, “The containment of Iran is now this administration’s number-one priority.”

A major consideration in the Trump administration’s decision to focus on Iran is the growing realisation that Tehran’s involvement in countries such as Iraq, Syria and Yemen is having a profoundly destabilising effect on the region, one that, if left unchecked, could result in a serious escalation in regional tensions.

This week’s decision by Russia to upgrade its anti-missile defences in Syria, for example, is directly related to Iran’s attempts to deepen its military footprint in the country. The Russian move is in response to the shooting down of a Russian aircraft by Syrian government forces, which believed they were aiming at Israeli warplanes attacking an Iranian missile site.

Consequently, if Israeli warplanes seek to launch further attacks against Iranian targets in Syria, they face being shot down by the Russians, a move that could have serious repercussions far beyond the confines of the Middle East.

It is a similar situation in Yemen, where Iran has artfully managed to attribute most of the blame for the humanitarian disaster currently afflicting the country on the Saudi-led coalition. This particular narrative, which has been readily accepted by media organisations such as the BBC, completely ignores the fact that Iran helped to start the conflict in the first place by supporting the Houthi rebels to overthrow the country’s democratically elected government. It also sustains the conflict with regular arms supplies, including the missile systems used to launch attacks against Saudi Arabia.

Given Yemen’s proximity to one of the world’s main shipping lanes, any further escalation of hostilities could result in a major disruption of world trade.

The Trump administration is simply not prepared to tolerate this level of Iranian disruptiveness, especially as much of it is aimed against key American allies in the Gulf. So the ayatollahs are now faced with two options: either they rein in their military interventions in the Arab world, or they face the consequences of provoking Washington’s ire.

Con Coughlin is the Daily Telegraph’s Defence and Foreign Affairs Editor and author of Khomeini’s Ghost