Watch video of the speedboat incident

When the White House announced that President Bush would travel to the Middle East this week to bolster support among America’s vulnerable Arab allies in the Gulf, there was always the risk that militants in the Iranian regime would feel forced to respond.

In Tehran the Gulf is known as the “Persian Gulf” and nothing could be calculated to upset the regime more than Mr Bush’s unprecedented five-day procession through the oil-rich region, where America maintains 40,000 troops, besides the forces deployed in Iraq.

From Friday the US leader will work his way down the Gulf states, starting in Kuwait and travelling to Bahrain, Abu Dhabi, Dubai and Saudi Arabia. Overhead, US fighters will be stepping up patrols to protect Air Force One, while below the warships of the US Fifth Fleet will be ready to respond to any Iranian moves.

For this reason, commanders in the naval wing of the Iranian Revolutionary Guards Corps (IRGC) may have been ordered or encouraged to cause mischief in the Strait of Hormuz, the narrow passageway at the entrance to the Gulf through which 25 per cent of the world’s crude oil is shipped.

The IRGC is one of the most powerful institutions in Iran, and one of its most celebrated former members is none other than President Ahmadinejad. The force was responsible last year for the ambush and capture of 15 British sailors and Marines, who were paraded on television and held for two weeks before being freed, humiliated but unharmed.

The IRGC regards the Gulf waters as its own and feels that it has the right to patrol at will. With Mr Bush expected to step up his rhetoric against Iran during his visit, Tehran may have wanted to remind him – and the world – about the vulnerability of global energy supplies, particularly with crude oil selling for $100 a barrel.

There is also the temptation to tweak the tail of the world’s only superpower. A year ago Mr Bush deployed two aircraft carrier battle groups in the Gulf and threatened to use force against Iran to prevent the country acquiring nuclear weapons. Many in the region believed that confrontation was inevitable.

Now Mr Bush is weakened as his presidency enters its final year. A US National Intelligence Estimate published last month revealed that Washington believes that Iran has suspended its atomic weapons programme. The threat of the use of force against one of the origial “axis of evil” regimes has evaporated.

Domestic politics in Iran may also have played a part in the Hormuz incident. The Iranian regime may have felt compelled to act in the increasingly tense political climate ahead of parliamentary elections in March, where the ruling hardliners are facing a stiff challenge from more moderate forces.

The Iranian mission was carried out by five IRGC speed boats that “swarmed” a US Navy cruiser, a destroyer and a frigate. The confrontation was hardly an even match. Each of the multimillion-dollar US warships could have destroyed the Iranian craft in seconds.

But that does not diminish the seriousness of the incident. Ever since the USS Cole was rammed by an al-Qaeda suicide boat in Aden harbour in 2000, killing 17 US sailors, US forces have been trained to use lethal force to prevent such attacks.

As many Iranians remember only too well, accidents can happen in the crowded air and waterways of the Gulf.

In 1988 the USS Vincennes shot down an Iran Air passenger jet, killing 290 people, after mistaking the aircraft for an Iranian fighter-bomber.

After three decades of separation from the West, Iranian motives and actions are never easy to interpret. Sunday’s incident is particularly curious because it came after a speech last week by Ayatollah Ali Khamenei, Iran’s supreme leader, who raised the possibility of one day restoring relations with the “Great Satan”, as America is commonly known by the regime.

“I would be the first one to support these relations,” Ayatollah Khamenei told students in the central Iranian province of Yazd. “Of course, we never said the severed relations were for ever.”

But he added that no one should expect any improvements soon. “For the time being, it [restoring ties] is harmful and we should not pursue it.”

Sunday’s incident in the Gulf will serve to remind those running in the US presidential elections that, for the next incumbent of the White House, resolving the festering relations with Iran remains one of America’s foreign policy priorities.

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