North Korea renewed its demand Tuesday for recognition as a nuclear power, saying it was a pre-requisite for the start of any dialogue with the United States.

A commentary in the official Rodong Sinmun newspaper rejected as "totally unacceptable" a US demand that North Korea commit to abandoning its nuclear weapons and missile programme before any talks can begin.

Any meeting at the negotiating table must be "between nuclear weapons states", it said.

The United States has made it clear that it will never formally accept the North, which carried out its third nuclear test in February, as a nuclear power.

After a month of escalating military tensions on the Korean peninsula, Seoul, Washington and Pyongyang have begun skirting around the possibility of dialogue.

For the moment, however, most energy is being expended on rejecting each other's pre-conditions.

During a trip to Seoul, Beijing and Tokyo earlier this month, US Secretary of State John Kerry said Pyongyang must first prove it was serious about reining in its nuclear programme.

North Korea responded by demanding the withdrawal of UN sanctions and an end to all future South Korea-US joint military exercises.

First radioactive traces from NKorea nuke test
Vienna (AFP) April 23, 2013 - Possible radioactive traces from North Korea's February nuclear test have been detected for the first time, although it remains unclear what fissile material Pyongyang used, monitoring organisation CTBTO said Tuesday.

"The ratio of the detected xenon isotopes (xenon-131m and xenon-133) is consistent with a nuclear fission event occurring more than 50 days before the detection," the Comprehensive Test Ban Treaty Organisation (CTBTO) said.

"This coincides very well with announced nuclear test by the DPRK (North Korea) that occurred on 12 February 2013, 55 days before the measurement."

It added however that the discovery by a monitoring station in Japan could not help it answer the key question of whether Pyongyang used plutonium or uranium in the blast.

North Korea used plutonium in its 2006 and 2009 tests and any discovery that it used highly enriched uranium for its third test would mark a significant technological step for the impoverished and unpredictable regime in Pyongyang.

It would also raise international concerns that North Korea might pass on weapons-grade uranium, or the necessary technology and knowhow to make it, to other "rogue states" or "terrorists" seeking to make crude nuclear explosive devices.

It is also possible that the so-called radionuclides were from a nuclear reactor or other atomic activity, and the CTBTO said it is currently examining the traces to see whether this is the case.

It ruled out however that the source was Japan's crippled Fukushima nuclear plant.

The detection was made at Takasaki, Japan, 1,000 kilometres (620 miles) from the North Korean test site. Lower levels were picked up at Ussuriysk, Russia, one of several hundred sites worldwide reporting to the CTBTO.