The capture of 15 British troops by Iranian forces in the northern Gulf was an international incident waiting to happen.

For weeks now tension has been building between Tehran and its critics in the West, both on the ground along the Iran-Iraq border area and over Iran’s controversial nuclear programme.

There is strong evidence that the capture of the Royal Marines and sailors from HMS Cornwall, on patrol in the northern Gulf, was a deliberate move by the Iranians to take pre-emptive action against its detractors.

All week diplomats have been finalising the text of a UN Security Council resolution that would impose a new set of sanctions against Iran to follow measures adopted in December.

They include: a ban on all arms exports; a freeze of assets abroad belonging to 28 people and institutions, including members of the Revolutionary Guards; and a curb on financial loans to the Iranian government.

Sir Emyr Jones-Parry, the British envoy to the UN, said he hoped the Council would pass the new resolution on Saturday.

At the same time, the US Navy has been building up its strength in the Gulf, with the arrival of a second aircraft carrier battle group. The muscle-flexing has been accompanied by warnings from Washington that the Bush Administration is still prepared to use force to stop Iran building an atomic weapon.

At the heart of the dispute is Iran’s programme of uranium enrichment, which the international community has demanded that it halts, suspecting that it could be a cover for building fissile material needed for an atomic warhead.

The Iranians have insisted that they plan to push ahead with their nuclear efforts regardless.

On Wednesday the Ayatollah Ali Khamenei, Iran’s supreme leader, gave warning that he would not hesitate to hit back if attacked. He described any UN moves as “illegal actions” and said Iran “can also carry out illegal actions and we will do that”.

His threat came as no surprise to British commanders serving in southern Iraq. They told The Times earlier this year that Iran was arming, financing and training Shia militias responsible for attacking British forces. They noted that attacks tended to peak at the same moment that diplomatic action was taken against Iran.

“We haven’t found any ‘smoking gun’ but certainly all the circumstantial evidence points to Iranian involvement in the bombings here in Basra, which is disrupting the city to a great extent,” Lieutenant-Colonel Justin Maciejewski, the commander of British forces in Basra city, told the BBC yesterday.

British officials will be hoping that the incident involving the capture of the marines and sailors can be settled peacefully. In 2004 a similar incident occurred and all British forces were freed, although their vessels remain in Iranian hands.

This time the stakes are higher and diplomatic relations far more strained.

Rasoul Movahedian Attar, the Iranian ambassador to London, is being summoned to the Foreign and Commonwealth Office later today for a dressing down by a senior official and similar protests will be made in Tehran.

The fear must be that the fate of the British servicemen will now be connected to what happens at the UN with regards to the resolution against Iran.

The incident risks turning an already tense situation explosive.

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• Charles blazes trail as sun king
• Thalidomiders win payout 50 years on
• Libel gag on talk of 'medical hurricane'