North Korea has threatened to demonstrate its nuclear deterrence in a move analysts say could indicate the regime is preparing to carry out a fourth atomic test amid long-stalled disarmament talks.
The National Defence Commission (NDC), chaired by leader Kim Jong-un, said on Friday that the North would continue efforts "to bolster up its nuclear deterrence for self-defence".
"And additional measures will be taken to demonstrate its might one after another as long as the US nuclear threat and blackmail persist as now", it said.
North Korea and its main ally China want a resumption of six-party talks on the North's nuclear weapons programme, but Washington and Seoul both insist that Pyongyang must first demonstrate a commitment to abandoning nuclear weapons.
"The US had better roll back its worn-out hostile policy towards the DPRK (North Korea) as soon as possible and shape a new realistic policy before it is too late," the NDC added.
"This would be beneficial not only to meeting the US interests but also to ensuring the security of its mainland."
In March last year, North Korea put its "strategic" rocket units on a war footing and threatened to strike targets on the US mainland, Hawaii, Guam, and South Korea as tensions soared.
Despite a successful long-range rocket launch in December 2012, most experts believe North Korea is years away from developing a genuine intercontinental ballistic missile that could strike the mainland United States.
Analysts in Seoul said the NDC statement indicated North Korea was mulling three options - a fourth nuclear test, the firing of a long-range rocket and the unveiling of progress in its programme of enriching uranium.
North Korea carried out nuclear tests in 2006, 2009 and in February last year.
"This warning is not about an imminent action but an expression of frustration with Washington, which refuses to budge an inch," Professor Yang Moo-jin of the University for North Korean Studies said.
Professor Kim Yeon-chul of Inje University said the North might consider carrying out a test using enriched uranium it has been developing for two years.
The NDC stressed the North would never make a first, unilateral move towards giving up its nuclear weapons programme despite US pressure to do so.