North Korean leader Kim Jong Un said the country's "nuclear warheads need to be ready for use at any time," the North Korean state news agency KCNA reported Friday.
"Under the extreme situation that the U.S. Imperialist is misusing its military influence and is pressuring other countries and people to start war and catastrophe, the only way for our people to protect sovereignty and rights to live is to strengthen the quality and quantity of nuclear power and realize the balance of power," Kim said, according to KCNA.
The news agency also confirmed the test-fire of a new multiple launch rocket system. It's unclear whether that event is the same launch by North Korea of "short-range projectiles," announced one day earlier by the South Korean Joint Chiefs of Staff.
"We are aware of the reports. We are closely monitoring the situation on the Korean Peninsula in coordination with our regional allies," the Pentagon said in response to Friday's news. "We urge North Kore a to refrain from provocative actions that aggravate tensions and instead focus on fulfilling its international obligations and commitments."
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'A lot of bluster'
North Korea is believed to have an untested capability when it comes to nuclear weapons. As one U.S. official told CNN's Barbara Starr, the regime has tested nuclear devices that it says have been miniaturized.
The attitude of U.S. officials is that they consider North Korea's claim true because they can't risk underestimating it, but the claim is not verified.
North Korea has also tested long-range missiles but not completely. It has not tested missile re-entry, for example. Additionally, North Korea has not married a nuclear device with a long-range missile, and the United States does not know whether North Korea would do so without testing first.
"The threat here is, to me right now, it's a lot of bluster," said Philip Yun, executive director of the Ploughshares Fund, a group that advocates nuclear disarmament. "For them to deliver on a threat, they have to have intent and they have to have capability. And quite frankly, I don't think they have both."
Yun told CNN the purpose of the news might be internal.
"Kim Jong Un has got a large party congress that's going to be happening in May. And this is all about, for him, again, additional consolidation of power. He'll want to get rid and justify getting rid of any enemies he may have.
"And this is part of a process where he is able to ratchet up the pressure, increase his control internally, and brandish his credentials to be 'protecting the motherland.' And so all of this sort of helps him internally even though it may not ring true to many of us here outside," he said.
Yun stressed that he does not think the North Koreans are suicidal: "They know that if they did a pre-emptive attack or used nuclear weapons, they would cease to exist."
Fresh sanctions
Earlier this week, the U.N. Security Council voted to impose an array of sanctions against North Korea because of that nation's recent nuclear test and missile launch, both of which defied international sanctions.
The U.N. resolution that brought about the sanctions aims to cripple the economic factors that fuel North Korea's nuclear and ballistic missile programs.
The North Korean state news agency blasted the sanctions as "unprecedented and gangster-like."
The "political and economic pressure and military aggression on the DPRK have gone to a grave phase that can no longer be overlooked," KCNA said.
China reiterated its opposition on North Korea developing nuclear weapons.
Fu Ying, a spokeswoman for China's Parliament, said it will abide by the Security Council sanctions, but she highlighted the need for six-party talks to resolve the issue.
Hydrogen bomb
Discussions about new sanctions started after North Korea claimed to have successfully tested a hydrogen bomb in January, its fourth nuclear test.
Then, in February, Pyongyang said it had successfully launched an Earth satellite into orbit via the long-range Kwangmyongsong carrier rocket.
According to CNN's Paula Hancocks, Friday's developments are not necessarily new, but they do represent an increase in the tensions that already existed on the Korean Peninsula.
"And, also bear in mind, we're just a couple of days away now from the joint military drills between the United States and South Korea. These happen every year. Washington and Seoul say they're defensive in nature, but every year they irritate Pyongyang," she said.
CNN's Catherine E. Shoichet contributed to this report.
