The recent U.S. beef shipment that violated Japanese import controls was an isolated incident and not a sign the American food system is unsafe, U.S. agricultural officials said Tuesday after meeting with their Japanese counterparts.

The officials were in Tokyo to reassure the government about American food safety standards after Japan halted U.S. beef imports over fears of mad cow disease last week when inspectors found banned spine bones in a recent shipment of U.S. veal.

J. B. Penn, U.S. undersecretary for farm and agricultural services, said the firm that exported the meat, Brooklyn-based Atlantic Veal & Lamb, had apparently not had enough experience in dealing with international customers. He pledged Washington would come up with steps to prevent a recurrence.

"We believe this was an isolated incident," Penn told reporters at the U.S. Embassy. "We have, like Japan, one of the safest food systems in the world."

The fresh halt in imports came only a month after Japan eased a two-year-old ban on U.S. beef, allowing meat from cows aged 20 months or younger but prohibiting parts such as brains and spine bones, which the Japanese consider at risk for mad cow disease.

Tokyo originally closed its market in December 2003 after the discovery of the first case of mad cow disease in the American herd. Mad cow disease, also known as bovine spongiform encephalopathy, or BSE, is linked to the rare and fatal human brain disorder, variant Creutzfeldt-Jakob Disease, which has killed over 150 people, most of them in the United Kingdom.

Japanese officials have been especially critical of the American inspection system and have refused to reopen the market until the mishap is fully investigated and Washington comes up with sufficient countermeasures.

Reflecting sensitivities in a country where many consumers were against renewing American imports, Prime Minister Junichiro Koizumi faced grilling in parliament on Tuesday over whether he reopened Japan's market too soon in a bid to please Washington.

Koizumi denied that.

"We decided to resume imports after scientific discussions by the Food Safety Committee and a report which took into consideration of people's opinions," he said. "The decision was not made because we put priority on the Japan-U.S. relations."

Also Tuesday, Japan confirmed its 22nd case of mad cow disease in a 5-year-old cow that died last week, the farm ministry said. The cow was not raised for food and posed no danger to Japanese beef, the statement said.

The U.S. has had two confirmed cases of the disease, but only tests a sample of its herd, while Japan carries out mad cow tests on all cattle slaughtered for food, as well as all cattle 24 months or older that die of other causes.

Penn, joined by other U.S. agriculture officials, said he expressed U.S. regret over the mishap in his meetings on Tuesday, and said Washington would thoroughly investigate how it happened and come up with preventative steps. All that information, he said, would be shared with the Japanese government.

The banned spinal bones were found on Friday in a package of veal sent by Atlantic Veal & Lamb. The Japanese government on Monday announced it had ordered inspections of all American beef imported since the previous ban was eased on Dec. 12.

Japan also resumed imports of Canadian beef on the similar conditions in December. On Monday, however, Canada announced that a cow from an Alberta farm had tested positive for mad cow disease, its fourth case since May 2003. Japanese officials said Tuesday they were studying the case and had not yet decided whether imports into Japan would be affected.

The 2003 ban on U.S. beef was sparked by the first discovery of mad cow disease in the American herd. Prior to that, Japan had been U.S. beef's most lucrative overseas market, buying some $1.4 billion worth in 2003. Under the agreement reopening the market last month, Japan accepted meat only from cows aged 20 months or less.

The fresh halt came just as U.S. officials were mounting an effort to get Japan to raise the age of cows from which it would accept beef.