Iran's sea trade buckles under Western sanctions

Of that total, the number of visits by container ships - which carry consumer goods ranging from foodstuffs and household items to clothing and toys - was 86 so far this year, compared with 273 for the whole of 2011 and 378 in 2010.

The world's top container firm Maersk Line said this week it had stopped port calls to Iran, citing the risk of damaging trade opportunities especially in the United States.

"Lower shipping volumes may also mean that importing vital commodities will be increasingly hard, leading to possible riots over inflation," said Alan Fraser, Middle East analyst with security firm AKE.

Only eight refrigerated cargo vessels carrying fresh produce including bananas called at Iranian ports so far this year, down from 16 in 2011 and 36 in 2010, the IHS Fairplay data showed. Even fishing trawlers unloading their catch have slumped to five from 14 last year and 20 in 2010.

Starved of dollars as the sanctions curb oil exports, Iran bought large amounts of grain earlier this year using other currencies. Nevertheless dry bulk ships, which can carry cereals and commodities such as coal and iron ore, have also made fewer port calls with 100 arrivals so far compared with 352 in 2011 and 406 in 2010.

"You start to see Iran reaching a balance of payment crisis particularly on the imports side when a plummeting currency, which makes imports exceedingly expensive, is compounded by external sanctions," said Mark Dubowitz with the Washington-based Foundation for the Defense of Democracies.

"The combination of these factors is making it difficult for Iran to buy what it needs from abroad and pay for these goods and services," said Dubowitz, who has advised U.S. President Barack Obama's administration and U.S. lawmakers on sanctions.

"ALMOST A BLACK HOLE"

Official Iranian data is not readily available and officials in the country could not be reached for comment. Iran's fleet has taken steps to camouflage its sea trade to discourage foreign attention.