Japan halted imports of U.S. beef on Friday, one month after lifting a ban, following the discovery of spinal material in a shipment that it said should have been removed to reduce the risk of mad cow disease, according to Reuters. U.S. officials immediately launched an investigation, ordered extra training for meat inspectors and sent a team of experts to examine shipments detained in Japanese ports. "This is an unacceptable failure on our part to meet the requirements of our agreement with Japan," Agriculture Secretary Mike Johanns told reporters. The Japanese Agriculture Ministry said the ban would remain until it receives more information from the United States. Japanese Prime Minister Junichiro Koizumi said that Agriculture Minister Shoichi Nakagawa wanted the United States to act firmly. "Preserving food safety and security for the people is extremely important," Koizumi said. U.S. cattle futures fell on the news. The February live cattle contract LCG6 at the Chicago Mercantile Exchange settled 0.350 cent per pound lower at 95.775 cents, after falling as low at 94.800 cents earlier on Friday. Japan, the biggest foreign market for U.S. beef, first banned American beef after a case of mad cow disease in December 2003, halting annual trade of $1.4 billion. The two-year ban became an irritant in otherwise close and friendly U.S.-Japan relations. --More 23 23 Local Time 20 23 GMT