Japan is the U.S.' most lucrative export market and farmers argue, according to BBC, that their meat is safe and BSE (mad cow disease) clear.
In order to protect consumers from mad cow disease, according to the report, Japan only accepts meat from cattle that is less than 21 months old and carcasses that have had their spinal cords, vertebrae, brains and bone marrow removed.
The sudden reimposition of the ban happened after a 390kg shipment of meat from New York was found to have some of the banned material still attached.
"This is an unacceptable failure on our part to meet the requirements of our agreement with Japan," says US Agriculture Secretary Mike Johanns.
