Taiwan has rejected 9,000 tonnes of US wheat after residue from a prohibited agricultural pesticide was found in a recent shipment, a senior food safety official said on Sunday.

According to Hsieh Ting-hung, deputy director of the food safety department, customs officials discovered residue from malathion pesticide in a shipment of US wheat some 10 days ago.

According to the US Wheat Associates, Taiwan is the seventh-largest importer of US wheat, with annual imports of an averaged of about 1 million tonnes a year.

Hsieh declined to comment on reports of possible adverse reaction among suppliers caused by the rejection of the consignment as speculated in Taiwanese media. He said that the impact on wheat supply would be "minimal" and that he expected shipments of US wheat to continue.

The reports suggested that US shippers would baulk at sending wheat consignments to Taiwan, which is virtually reliant on imports to meet its milling needs, for fear of its cargo being rejected.

"For now, we hope that in future suppliers can meet our regulations," said Hsieh, who gave no further details on the plan.

Hsieh said that while Taiwan currently does not permit any detectable traces of the pesticide residue in wheat, the government was moving towards a policy of allowing small detectable amounts.

Reports quoted an official from the Taiwan Flour Mills Association, the island''s main wheat buying organisation saying, if suppliers baulked at offering to sell to Taiwan over this issue, it could lead to a shortage of flour by the end of August.

Codex Alimentarius, the international standards-setting body for pesticide residues, last year adopted new, sharply reduced tolerances for malathion residues on wheat and wheat flour.

The new standards permit 0.5 ppm and 0.2 ppm, down from the previous tolerances of 8.0 ppm and 2.0 ppm, said the associates.

The contaminated mid-gluten wheat was part of a 40,000-tonne shipment from the United States, said a report in the Liberty Times on Saturday.

The report pointed to a failed tender last week by the group to secure suppliers for a nearly 90,000-tonne shipment due for delivery at the end of August because of supplier reluctance.

Traders and officials had said the tender failed due to price considerations