N Korea wants Japan out of talks
North Korea agreed to halt nuclear activity in 2007
North Korea has suggested that Japan be removed from long-running six-party talks aimed at its nuclear disarmament.
A commentary in a Pyongyang newspaper said Japan kept creating trouble and had "obstructed" the process.
Japan has refused to grant North Korea the economic and energy aid it seeks as part of a negotiated agreement.
Tokyo says Pyongyang has failed to properly investigate the fate of Japanese citizens it abducted in the 1970s and 1980s.
South Korea has said that an outside donor may need to be brought in to provide Japan's share of aid.
However the US remained optimistic that the situation could be resolved.
"I think there's a high degree of confidence among the five that we will meet our obligations," State Department spokesman Sean McCormack said.
The countries involved in the six-party process are North and South Korea, Russia, China, Japan and the US.
The six nations reached an agreement in February 2007, in which North Korea agreed to halt all its nuclear activity in exchange for aid and other concessions.
Snatched in the '70s and '80s
Used as cultural trainers for N Korean spies
Five allowed home in 2002
Five children now freed from N Korea
Eight said to be dead, others missing
Pyongyang was to receive one million tonnes of energy aid from the five other countries in return for disabling its nuclear plants. It began dismantling its main nuclear complex last November, and blew up the main cooling tower in a symbolic gesture of its commitment to the process.
A row which threatened to derail the accord was narrowly averted last week, when the US announced it was removing Pyongyang from its list of state sponsors of terrorism.
Pyongyang wanted to be removed from the list in order to receive international aid and loans, and facilitate its diplomatic rehabilitation.
But Japan criticised the move as "extremely regrettable", saying it wanted North Korea to provide more information about Japanese abductees before Pyongyang was removed from the list.