The powerful 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 added in a statement carried by Pyongyang state media.
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 some tangible 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 statement 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's military put its "strategic" rocket units on a war footing and threatened to strike targets on the US mainland, Hawaii and Guam, as well as 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 inter-continental ballistic missile that could strike the mainland United States.
Analysts in Seoul said the NDC statement on Friday 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.
- 'Expression of frustration' -
"This warning is not about an imminent action but an expression of frustration with Washington, which refuses to budge an inch despite Beijing's efforts to draw it back to dialogue", Professor Yang Moo-Jin told AFP.
Professor Kim Yeon-Chul of Inje University said the North might consider carrying out a test using enriched uranium it has been developing for the past two years in addition to its plutonium-based weapons.
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.
The statement also lambasted what it called a "groundless human rights racket" against the North by the United States.
Robert King, the US special envoy on North Korean human rights, said the United States supported UN action on North Korea's human rights record after a hard-hitting UN report last month compared the regime's treatment of its people to the Holocaust.
He voiced confidence that the UN Human Rights Council would pass a resolution on the totalitarian state's record at its session this month in Geneva.
In a 400-page report last month, a UN Commission of Inquiry documented extermination, enslavement and sexual violence by North Korea. The commission's Australian chairman Michael Kirby drew a parallel with the Holocaust and demanded international action.
But China holds veto power on the Security Council and has publicly rejected referring the leaders of North Korea, its ally and neighbour, to the International Criminal Court for trial.