Japan wants all slaughtered cows in the United States to be tested for mad cow disease before U.S. beef is again imported into the country, but the U.S. Agriculture Department is resisting, which has prompted the wife of the U.S. ambassador in Japan to get involved.

The issue of mad cow testing has resulted in a public tiff between President Bush's agriculture secretary and the wife of his ambassador to Japan.

Agriculture Secretary Ann Veneman has rebuffed small meatpackers who want to test all cattle they slaughter for mad cow disease, so they can resume exporting beef to Japan and other countries. Mad cow, or bovine spongiform encephalopathy, is thought to cause a fatal brain disease in humans. Japan has barred U.S. imports since December, after at least one cow in the U.S. was found to have the disease.

The Department of Agriculture argued that testing by small slaughter houses would give the false impression that untested beef is not safe.

However, Nancy Kassebaum Baker, the wife of the U.S. ambassador to Tokyo, James Baker, disagrees. She sent a letter to Ms. Veneman about the issue, and she discussed her concerns in Tokyo.

"I could not understand and I really still do not, the case made for not letting them do it does not seem to me to be that valid," she said. "Why meatpackers who wish to have the [BSE] testing facilities and the ability to do 100 percent testing of the cattle for consumers in Japan, who wish to have that requirement, at this point can not go ahead and do it?"

Mrs. Baker said that the agriculture secretary had not responded to her letter.

Ms. Veneman accuses Mrs. Baker, a former Kansas senator who owns cattle, of acting out of self-interest. The secretary said that Mrs. Baker's family has a business relationship with Creekstone Farms, which is the first U.S. slaughterhouse to set up its own mad-cow testing facility.

Mrs. Baker added that the agriculture secretary has the facts wrong.

"Neither my son nor I - because I have cattle as well - have ever sold cattle to Creekstone," she said. "We have always sold at public auction to the highest bidder. So there is no interest in our part other than what I see it doing to ranchers in my state of Kansas, just as well as elsewhere."

Kansas relies heavily on agricultural exports, particularly beef, for its economy. Critics say the U.S. government is listening only to big meat companies, which control 80 percent of the U.S. industry.

Japan's Agriculture Ministry said that Tokyo will not budge on its demand that all U.S. cattle be checked for BSE and that the testing be certified by the U.S. government. U.S. and Japanese officials have pledged to settle the issue of beef imports within a few months.