Tokyo dismissed Pyongyang’s complaints saying that that North Korea has failed to properly investigate the fate of Japanese citizens it abducted in the 1970s and 1980s.
Japan is one of the countries involved in the six-party process; the others are North and South Korea, Russia, China and the United States.
All six reached an agreement in February 2007, in which North Korea agreed to halt all its nuclear activity in exchange for aid and economic concessions.
Things appeared on the verge of collapse a few weeks ago so much so that there were fears that North Korea would restart its nuclear programme.
This was narrowly averted last week, when the US announced it was removing Pyongyang from its list of state sponsors of terrorism.
The US move finally opened the doors to international aid and loans, and will facilitate the North’s diplomatic rehabilitation.
But Japan criticised it as "extremely regrettable", saying it wanted North Korea to provide more information about Japanese abductees.
South Korea's president Lee Myung-bak said that Kim Jong-il is still in control of North Korea despite rumours about his health and a possible operation in August.
In an interview with French daily Le Figaro he said that “despite what is said or written about Kim Jong-il’s health, we see the situation in the North as normal.”
Furthermore, “I cannot say whether the North Koreans have [nuclear] weapons or not,” but they are “technologically capable of producing” them, he added.