( CNN ) North Korea on Tuesday served up its latest round of threats against the United States , saying it plans to place military units tasked with targeting U.S. bases under combat ready status . The Supreme Command of the North Korean military said it `` will put on the highest alert all the field artillery units including strategic rocket units and long-range artillery units , which are assigned to strike bases of the U.S. imperialist aggressor troops in the U.S. mainland and on Hawaii and Guam and other operational zone in the Pacific , as well as all the enemy targets in South Korea and its vicinity . '' Angered by tougher U.N. sanctions and joint military exercises by the United States and South Korea , Pyongyang has issued a range of bombastic threats in recent weeks . North Korea 's threats : 5 things to know . The announcement this month by the United States that its B-52 bombers were making flights over South Korea as part of the military exercises particularly enraged the North , which warned of reprisals if the sorties continued . The North Korean military statement Tuesday , carried by the state-run Korean Central News Agency , referred to the B-52 flights again , saying they had taken place over South Korea on Monday . The U.S. Department of Defense responded to the North 's latest saber-rattling by reiterating its confidence that it can fend off whatever the regime of Kim Jong Un can come up with . `` The U.S. is fully capable of defending ourselves and our allies against an attack '' by North Korea , said Lt. Jack Miller , a Pentagon spokesman . `` We are firmly committed to defending the Republic of Korea and Japan , '' he added , using the official name for South Korea . Island faces North Korean threat up close . U.S. and South Korean generals on Friday signed a new contingency plan `` designed to counter future North Korean provocations . '' Military officials from the two allies developed the plan after North Korea shelled South Korea 's Yeonpyeong Island in 2010 , killing four people . Weeks of saber-rattling . The slew of fiery rhetoric from Pyongyang in the past few weeks has included threats of pre-emptive nuclear strikes against the United States and South Korea , as well as the declaration that the armistice that stopped the Korean War in 1953 is no longer valid . Most observers say North Korea is still years away from having the technology to deliver a nuclear warhead on a missile , but it does have plenty of conventional military firepower , including medium-range ballistic missiles that can carry high explosives for hundreds of miles . Behind the veil : A rare look at life in North Korea . The heightened tensions on the Korean Peninsula came after the North carried out a long-range rocket launch in December and an underground nuclear test last month , prompting the U.N. Security Council to step up sanctions on the secretive regime . The North Korean statement Tuesday also referred to the sinking of a South Korean warship , the Cheonan , which took place three years ago to the day , killing 46 sailors . South Korea blamed the North for the attack , accusations that Pyongyang has repeatedly denied . `` The present South Korean puppet authorities tried to link the Cheonan sinking case with the DPRK and shift the blame for the Yeonpyeong Island shelling on to the DPRK , '' the statement said , using the shortened version of the North 's official name , the Democratic People 's Republic of Korea . U.N. human rights inquiry angers North Korea . CNN 's Judy Kwon contributed to this report .
South Korea says it has its military units ` ` on the highest alert '' It says the units hit targets on the Korean mainland , Hawaii and Guam . The U.S. says it is ` ` fully capable '' of defending itself and its allies . The North is angry over U.N. sanctions and U.S.-South Korean military exercises .