Iran's confrontational attitude towards the rest of the world is costing the country dearly in lost trade and investment, according to a letter signed by 60 economists published on Saturday.

The open letter, the latest broadside against president Mahmoud Ahmadinejad, denounced the "heavy price paid by the country over the negative consequences of government policy."

In particular, it spoke of the "misguided trade policy and the policy of tension with the rest of the world, which has deprived Iran of opportunities for trade and foreign investment."

It said the sanctions imposed by the UN Security Council over Iran's refusal to halt uranium enrichment had added billions of dollars in extra costs to the country's foreign trade.

The letter, signed by economists from major universities around the country, criticises what it calls "extremist idealism," an "undue haste in acting" and the "absence of cost assessment on economic programmes."

The economists also warn that the current global economic crisis "will impose heavy costs on the country," while also pointing out that government finances will be severely hurt by the precipitous recent drop in oil prices.