DENVER -- Creekstone Farms Premium Beef announced plans to challenge the U.S. Department of Agriculture's decision to maintain a ban on voluntarily tests for bovine spongiform encephalopathy by privately owned beef processors. The company said it is pursuing legal and political options to challenge the government's authority to control domestic sales of BSE diagnostic tests, and its decision to prohibit Creekstone from testing cattle at its Arkansas City, Kan., plant. Creekstone officials said they're willing to test more cattle at a lower cost than the USDA. Like other beef processors, Creekstone officials want to see Japan lift its BSE-related ban on American beef. Officials in Japan have demanded 100% testing of all beef bound for their market as a requirement prior to resumption of trade. The USDA plan tests only cattle older than 30 months, and officials have contended that universal testing is not necessary because BSE has never been detected in younger cattle. Last week, Japan's vice agriculture minister called the government's decision not to accept Creekstone's offer "regrettable." A U.S. delegation is to travel to Japan later this month to resume talks aimed at breaking the impasse. The discovery in December of the first U.S. case of mad cow continues to be felt within the beef industry. Creekstone is losing a minimum of $200,000 in revenue every day, and the company will continue to track losses to determine damages, officials said. Meanwhile, Mexico announced it would partially drop its ban on U.S. imports, and open the border to a larger array of American beef products, including trimmings, liver and other items.