(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.

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.

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the United States and South Korea, as well as the declaration that the armistice that stopped the Korean War in 1953 is no longer valid.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.

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.

"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.