The US Agriculture Department said advanced tests on brain samples from the apparently 10-year-old cow identified the fatal disease. The cow was singled out last weekend.

The discovery came while US officials were trying to convince Japan to reopen its market to US beef after a shipment of veal violated meat export rules by containing spinal material. Japan suspended beef trade on January 20.

The Republic of Korea on Monday said it could cancel a planned opening of its market in April to US beef if a new US case was found. Seoul has banned US beef since the first US case in December 2003.

Consumer advocacy groups called for stricter testing. But industry officials said US safety measures were adequate, and noted that Americans have actually increased their consumption of beef in the past couple of years.

The United States has struggled to restore beef exports to overseas markets that totaled US$3.8 billion annually before mad cow was discovered. Beef exports in 2006 are estimated at 905 million pounds, down 64 percent from 2003.

Reuters