TOKYO/WASHINGTON (Reuters) - Japan halted imports of U.S. beef on Friday

 just a month after lifting a ban, following the discovery of spinal material in a shipment that should have been removed due to the risk of mad cow disease. U.S. officials immediately launched an investigation and ordered extra training for all American meat inspectors, surprise inspections at plants handling beef exports, and sent a team of experts to examine meat shipments now held 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.

U.S. cattle futures fell on the news. The February live cattle contract was down 0.825 cent at 95.300 cents a pound in early trading on the Chicago Mercantile Exchange. Japan first stopped all purchases of beef from the United States after a case of the brain-wasting mad cow disease in December 2003, halting annual trade worth about $1.4 billion.

The ban lasted two years and became an irritant in otherwise close and friendly U.S.-Japan relations. -- full story: