* Sales hike comes after Japan relaxes import rules * Rules were put in place after US mad cow disease By Theopolis Waters CHICAGO, Feb 22 U.S. beef export sales to Japan soared to the highest in more than two years last week following Tokyo's decision to ease import rules related to the outbreak of mad cow disease in 2003, government data showed on Friday. Japan, once the top market for U.S. beef, on Feb 1 began allowing U.S. beef imports from cattle up to 30 months old, a minimum risk for the disease. A complete ban on beef imports was lifted by Japan in 2006, when it allowed beef from cattle 20 months or younger. The U.S. Department of Agriculture's weekly export sales data on Friday showed Japan, the world's largest beef importer, bought 10,900 tonnes in the week ended Feb. 17, the most since 12,497 tonnes in the week ended Dec. 23, 2010. Total U.S. beef sales last week to all destinations were 22,200 tonnes, the most since 23,500 tonnes during the week of April 12, 2012. Increasing the age limit allows leading U.S. beef processors such as Cargill Inc, Tyson Foods and JBS USA Holdings Inc to compete for market share lost primarily to Australia. Chicago Mercantile Exchange live cattle futures were higher on Friday, due in part to news of the strong beef sales to Japan. The timing of Japan's purchases also comes when beef prices in the United States are reaching record highs, as the worst drought in more than half a century reduced the herd to the smallest in 61 years. U.S. government monthly data showed the retail price of beef hit a record high in January at $5.24 per lb. It was up from the December price of $5.11 and surpassed the previous all-time high of $5.15 set in November.