Iran visit may help US ties

US relations with Iran were severed in 1979

As British Foreign Secretary Jack Straw prepares to visit Iran, BBC Teheran correspondent Jim Muir examines the significance of his groundbreaking trip.

Jack Straw's surprise announcement shows how much the current crisis is moving things rapidly on.

Jack Straw is keen to improve relations between Britain and Iran

It has clearly provided an opening for Iran and Britain to move closer together and for Britain to act as a channel of communication with its close ally, the United States.

British officials are talking of a window of opportunity but it is an opportunity which may not last for long.

War is looming and the Americans are warning that all other nations have either to be with Washington or with the terrorists.

That presents a stark choice for Iran; its relations are bad both with the United States and with the Taleban.

Anti-terror coalition

Mr Straw's visit comes in the context of western coalition building.

Iran, however, can clearly not simply jump on an American bandwagon without any other consideration.