North Korea has said it was being forced to "re-examine" its nuclear programme because of fresh signs the US remains hostile towards the country, indicating it will step up defiant efforts to boost its nuclear arsenal.
"Various circumstances compel us to completely review the nuclear issue," the North's foreign ministry said in a statement released through the official Korean Central News Agency (KCNA) on Friday.
The North said it had no choice, accusing the US and neighbouring South Korea over a plot to blow up a statue of its founding leader.
"The consistent hostile policy towards the Democratic People's Republic of Korea (DPRK) pursued by the US is giving rise to the evil cycle of confrontation and tensions on the Korean Peninsula, making the prospect of de-nuclearising the peninsula all the more gloomy," the North's unnamed foreign ministry spokesman said on KCNA.
The plot amounted to a "war action" and ran counter to a deal under which Pyongyang agreed to dismantle its nuclear programme in return for economic and diplomatic benefits and security guarantees, the statement said.
It did not elaborate on what was meant by the review.
But it will add to concerns Pyongyang is planning to conduct a third nuclear test following its failed rocket launch in April - although last month the North said it had no plans "at present" to conduct such a test.
The new leadership of North Korea, headed by the third generation of the Kim family, re-inforced its control on the reclusive state this week by further promoting its young leader Kim Jong-un and purging a top general who was seen as opposing his reforms.
Kim became head of the military this month after sacking Vice Marshal, Ri Yong-ho, and was then named as the new defence chief.
The new threat comes after South Korea confirmed a man who was arrested in the North after allegedly attempting to blow up a statue of founding father Kim Il-Sung, was a former defector who had settled in the South.
Pyongyang claimed South Korean intelligence authorities had hired him to carry out the plot and that Washington was actively involved.
"Without the US fundamental repeal of its hostile policy toward the DPRK first, it will be completely impossible to settle the issue of ensuring the lasting peace and stability on the Korean Peninsula," the statement.
Meanwhile, North Korea's cabinet has created a so-called political bureau to take control of the economy from the military.
The move could indicate the nation's leader Kim Jong-un is preparing to make economic reforms.
The changes could herald the most significant reforms by the North in decades. Previous attempts at a more market driven economy have floundered, most recently a drastic currency revaluation in late 2009.