North Korea\'s military said Tuesday it plans to place strategic missile and artillery units on the highest alert to prepare for possible strikes on the US mainland.  \"From this moment, the Supreme Command of the Korean People\'s Army will put all of its field artillery into the No.1 combat ready posture, including strategic rocket units and long-range artillery units that will target the US mainland, Hawaii and Guam and other US military bases in the Pacific as well as South Korea,\" the Supreme Command said in a statement carried by the official Korean Central News Agency.  The announcement came as Pyongyang ratcheted up military threats to Seoul and Washington over their joint military drills this month, in which American B-52 bombers\' participated, and the tougher sanctions adopted by the UN Security Council against the North over its third nuclear test on February 12th. (end) mk.mb KUNA 261808 Mar 13NNNN