Thai farmers are gearing up for a new fruit harvest with their eyes on a big new market -- the United States, where they hope their tasty exotic produce can tempt American palates.

Last July the United States ended a decade-long ban and began allowing Thailand to sell fresh mangos, mangosteens, rambutans, lychees, longans and pineapples, provided the fruits are irradiated to kill the pests that nest in them.

"The US is considered a high potential market given its high purchasing power and huge population, which includes a large number of Asians" already familiar with Thailand's exotic fruits, said Boonmee Wongshotisatit, director of the Thai Fruit and Vegetable Producer Association.

"After more than 10 years of completely closing its door, now Thai fruits are allowed to enter the US market to compete with those from Mexico, Brazil and Australia," he told AFP. Boonmee's Asia Exotic Corp is among 18 Thai traders now allowed to export fruits to the US mainland.

The firm sent its first shipment of mangos and longans in November, but the real test will begin in May as harvests for tropical fruits get underway. The six fruits now allowed for export to the US are among Thailand's biggest crops. The kingdom produced over one million tonnes just of mangos last year, according to the Department of Agricultural Extension.

Thai fruits already sell in China, Japan, India, Taiwan and European countries such as Britain and Germany. "The US has greater potential because of its larger population, which includes more Asians and also Mexicans" who seek out exotic fruits, said director Chavalit Hunka from the department.

"However, continuous campaigns are needed to raise public awareness and to expose the market to Thai fruits," Chavalit told AFP. The agriculture ministry predicts exports of fresh fruits to the United States could reach 20,000 tonnes annually in a few years' time.

Mangosteens, which Thais call the "queen of fruit," are expected to make a particular splash in the United States, where it is becoming a popular health supplement despite the high cost and low supply.

With a purple shell encasing white flesh that tastes pleasantly sweet and sour, mangosteens also contain xanthone -- a type of antioxidant said to balance free radicals in the body that can cause cancer or heart disease.

Mangosteens originate in Southeast Asia, and the region is the world's major producer of the fruit. About 300,000 tonnes of mangosteen were produced in Thailand this year, more than twice as much as last year, according to Chavalit.

For farmers, finding a new market helps shore up prices when fruits flood the local market during the local harvest season. Prices of lychees, for example, sometimes drop to 10 baht (30 cents) a kilogram (2.2 pounds) from as high as 150 baht.

"Oversupply happens every year. If we have new buyers -- either local or abroad -- we can sell more lychees at better prices," said grower Lamyai Chaiyakit, 47, from central Samut Songkhram province. But growers say that selling to the United States is not a sure bet. Shipping is expensive and time-consuming, so the fruits are not fresh when they arrive.

"Sending fresh fruits to the US is costly, especially managosteens, which have thick and heavy shells," said Suwat Phewsa-ard, a mangosteen grower from eastern Trat province. "If Thai managosteens are available in the United States but at higher prices than our competitors, who is going to buy our fruit?" he told AFP.

There are also concerns over possible side-effects from the irradiation required for the US shipments. "Radiation may shorten the fruits' shelf-life and cause radiation burns that make the fruits less attractive," said Chusak Chuenprayoth, head of agricultural committee at the Thai Chamber of Commerce.