TEHRAN -- With its enduring relics of a glorious imperial past, spectacular glittering mosques and breathtaking landscapes, Iran lays claim to some of the finest cultural jewels in the Middle East.

But a potentially catastrophic collapse in the country's tourist trade is threatening to leave this dazzling array of attractions largely unseen by foreign eyes, as international tensions with the west deter a growing number of overseas visitors. The problem has been exacerbated by the recent detention of 15 British marines and sailors, which prompted mass cancellations of foreign tours to a land described this week by its president, Mahmoud Ahmadinejad, as a cradle of civilisation.

Fears of military conflict over Iran's nuclear programme and disquiet over Mr Ahmadinejad's infamous remarks on the Holocaust had already caused a sharp decline in the number of affluent western visitors, a vital source of foreign currency in a struggling economy.