TOKYO (AP) -- Japan confirmed its 14th case of mad cow disease Thursday, after a Holstein cow from northern Japan tested positive for the brain-wasting illness, a government official said.

The four-year-old cow from Shikaoi town in Hokkaido prefecture was found dead Saturday and experts who tested the animal confirmed Thursday it had mad cow disease, agriculture ministry official Hiroaki Ogura said.

The cow is the 14th in Japan to test positive for the disease -- formally known as bovine spongiform encephalopathy, or BSE -- since 2001 when Tokyo began checking every slaughtered cow before it entered the food supply.

Tokyo also has banned the use of meat-and-bone meal -- made from ruminant animal parts -- in cattle feed because it is believed to have led to previous outbreaks of the disease.

Ogura said officials were trying to trace the feed the animal had been given and other details about its recent habits. Officials also were monitoring some 220 other cattle at the same farm to prevent any potential spread of the illness, Ogura said.

The latest discovery came as Japan considers relaxing testing standards that could lead to a partial lifting of Japan's ban on U.S. beef imports.

Tokyo prohibited all U.S. beef from entering Japan last December after the discovery of a case of mad cow in the United States. It had insisted it wouldn't lift the ban until the United States also instituted blanket testing for cows.

But Japan showed signs of relaxing its demand last month when the state-appointed Food Safety Commission announced the country could import meat from untested cows 20 months old or younger without endangering public health.

Prime Minister Junichiro Koizumi told the legislature Wednesday he hoped for an early resolution to the trade dispute while ensuring Japanese consumers' safety.

Japan had been the most lucrative overseas market for U.S. beef and Japanese consumers had been drawn to the product, which is much cheaper than domestic beef.

Japan bought $1.2 billion US of beef in 2003, more than any other country, before it halted imports.

Eating beef from a diseased cow is thought to cause the fatal human variant Creutzfeldt-Jakob disease.

Hokkaido, Japan's northernmost main island, lies some 800 kilometres northwest of Tokyo.