British commanders fear reaction to American aggression

The allegations of US covert operations inside Iran have added to the worries in Whitehall that the stand-off with Tehran over its nuclear ambitions could be moving into a more dangerous phase.

Last summer’s capture of eight Royal Marines by Iranian Revolutionary Guards off southern Iraq has convinced many senior British officers and diplomats that any increase in tension with Iran would result in ‘blow back’ against British forces in Iraq. The marines were eventually released unharmed but it later emerged that Iranian gunboats entered Iraqi territorial waters to abduct the marines’ patrol boats.

Revolutionary Guard naval forces conducted the operation, apparently on the orders of hard-line Mullahs, causing tension within the Tehran government which had been trying to cultivate the Europeans as a counter-weight to the Americans. "We now think the Iranians were sending us a signal," said one British officer. "They were saying, if you get too close to the Americans we can make life very difficult for you and you will pay a price."

Foreign Office sources are particularly worried that the departure of Colin Powell from the Bush administration has left the neo-conservatives in control of US foreign policy in Washington. British intelligence sources are becoming worried that the Iranians will employ a strategy to strike back at US interests and its allies across the Middle East.

Here, the role of the large Shia population in southern Iraq will be crucial and this could make life very uncomfortable for the British garrison in the Basra region.

Until now the Shia of southern Iraq have generally been co-operative with British forces, but the fear is that Tehran could activate "sleeper" cells to launch an all- out guerrilla war.

There were credible reports that last summer Tehran concentrated troops along the border with Iraq in response to US sabre-rattling over the nuclear issue, raising the possibility that Iran might try to seize Iraqi territory.