TEHRAN, September 9, 2008 (AFP) - Iran's pistachio production is set to plunge by 60 percent because of a winter freeze, allowing the United States to take over as the world's top exporter, an official was quoted as saying on Tuesday.

'This September we will harvest at most 100,000 tonnes of pistachio nuts,' Mohammad Hossein Karimi-pour, who heads the agricultural commission in Iran's chamber of commerce, told Sarmayeh newspaper.

He said this year's crop was mostly affected by winter cold and that farmers should also expect 'a bad two years ahead due to water shortages, increased costs and inflation.'

Iran produced 280,000 tonnes of pistachio nuts in 2007, followed by its arch-enemy the United States with 185,000 tonnes, he said.

Pistachio nuts are Iran's third largest foreign currency earner and account for about 50 percent of total agricultural exports.