"Kim Jong Un knows that if war breaks out, he is one of the first casualties".
North Korea will remain committed to the country's nuclear development in 2018, according to a report released on Saturday by state-run news agency KCNA.
North Korea has finally agreed to give up its nuclear programme but with a condition that the United States (U.S.) and its allies should stop blackmailing it.
The aggressive tests have led to more global sanctions and pressure on North Korea amid concerns that the window for stopping or rolling back its nuclear program is closing rapidly.
"We have secured powerful deterrence against the nuclear threat from the USA", he added.
"We're actually closer in my view to a nuclear with North Korea and in that region than we've ever been and I just don't see how, I don't see the opportunities to solve this diplomatically at this particular point", Mullen said on ABC News' This Week.
The president vowed to destroy North Korea if the country continued to threaten the USA, speaking during his maiden speech at the United Nations earlier this year.
"We define this "sanctions resolution" rigged up by the USA and its followers as a grave infringement upon the sovereignty of our republic, as an act of war violating peace and stability in the Korean Peninsula and the region, and categorically reject the 'resolution, '" the statement released by the state-controlled Korean Central News Agency (KCNA) read.
"The DPRK, an undeniable new strategic state and nuclear power of Juche, declares: Do not expect any change in its policy".
Moscow has long called for the two sides to hold negotiations aimed at reducing tensions over the nuclear and missile programme North Korea is pursuing.
David Wright, a missiles expert at the Union of Concerned Scientists, said: "The question that has always been raised is: Did North Korea get this technology from a [Russian] fire sale?"