U.S. President Barack Obama said the U.S. could "destroy North Korea with our arsenals," but its proximity to ally South Korea should be considered in addition to humanitarian costs associated with such action.

Obama made the remark in an interview with CBS that aired Tuesday, talking about difficulties handling the communist regime that he described as "a massive challenge." Obama also called the North "erratic enough" and the country's leader, Kim Jong-un, "irresponsible enough that we don't want them getting close."

"But it's not something that lends itself to an easy solution," Obama told the interviewer, according to CBS. "We could, obviously, destroy North Korea with our arsenals. But aside from the humanitarian costs of that, they are right next door to our vital ally, Republic of Korea."

Obama also said that the top U.S. priority is to protect the American people and allies South Korea and Japan, countries he said "are vulnerable to the provocative actions that North Korea is engaging in."

"One of the things that we have been doing is spending a lot more time positioning our missile defense systems so that even as we try to resolve the underlying problem of nuclear development inside of North Korea, we're also setting up a shield that can at least block the relatively low-level threats that they're posing right now," Obama said.

On Sunday, Obama rejected North Korea's proposal to put a moratorium on nuclear tests in exchange for the U.S. suspending joint military exercises with South Korea that Pyongyang has long denounced as a rehearsal of invasion of the country.

Obama urged Pyongyang to show seriousness about its denuclearization commitment, saying that if it does so, the U.S. is prepared to "enter into some serious conversations with them about reducing tensions and our approach to protecting our allies in the region."

On Tuesday, the North's Foreign Ministry issued a statement claiming Saturday's test launch of a submarine-launched ballistic missile was "the exercise of the just right to self-defense" amid the "U.S. escalating threat of nuclear war."

"Now that the U.S. is rendering the situation extremely tense while persisting in hostile policy and nuclear threats to the DPRK, the only way for the DPRK to avert thermo-nuclear war on the Korean peninsula and the region is to ensure balance of force by dint of powerful nuclear deterrence," the ministry said.

"We will bolster the nuclear force pursuant to the Workers' Party of Korea's strategic plan to counter the nuclear weapons in kind no matter what others may say," it said. (Yonhap)