Japan's envoy says North Korea questioned Tokyo's role in 6-nation nuclear talks

North Korea cast doubt Monday on Japan's qualifications to participate in six-nation nuclear disarmament talks, Tokyo's chief envoy said, ratcheting up recent tensions between the two sides.

North Korea's top nuclear negotiator "questioned Japan's commitment to meet its requirements and also questioned its qualifications to remain a participant" in the six-nation discussions, which began a fresh round on Monday, said Kenichiro Sasae, Japan's representative.

North Korean envoy Kim Kye Gwan made the remarks at the opening session of the talks, which also include South Korea, host China, the United States and Russia, reiterating a position his government has stated before.

Sasae did not elaborate on what Kim said.

"I told them that their argument is totally off the mark and the question about our qualification is not worth a comment," Sasae told reporters. "I think nobody takes their argument seriously."

The top U.S. envoy to the talks, Christopher Hill, said he didn't think the dispute would obstruct negotiations, but urged North Korea to take the opportunity to improve ties with Japan.

"I feel (North Korea) needs to do more to square up its relationship with Japan," Hill said. "I would hope (North Korea) would understand what its interests are."

In Vietnam earlier this month, talks between North Korea and Japan on normalizing ties ended without any progress after Korean negotiators reacted angrily to Tokyo's insistence that they resolve questions about the North's abduction of Japanese citizens in the 1970s and 1980s before improving relations.

The discussions were part of working group meetings established under a landmark Feb. 13 agreement at the last round of nuclear talks. Under the pact, North Korea pledged to shut down its nuclear reactor in return for energy aid and talks on improved relations with regional powers, including Japan and the United States.

Japan has refused to provide energy and economic aid to North Korea or normalize ties unless it makes progress in resolving the abduction questions.

However, Japan does not believe its focus on the abduction issue is interfering in the six-nation process, a Japanese delegation member said on customary condition of anonymity. He added that other participants, especially the U.S., have supported Japan's position on the issue.

"It's clearly not up to North Korea to decide whether Japan participates or not," Japanese Prime Minister Shinzo Abe told reporters in Tokyo late Monday. "We must make sure North Korea takes concrete steps toward denuclearization as promised at these talks."

North Korean envoy Song Il Ho demanded in Vietnam that Japan take the first step instead of asking his country to make concessions, reports AP.

He said North Korea cannot consider reinvestigating the abduction issue until Japan lifts sanctions against the North over its missile and nuclear tests last year, stops "suppressing" pro-North Korean residents living in Japan, and agrees to reparations for its 1910-45 colonial rule over the Korean peninsula.

Japan has yet to formally apologize to North Korea for its wartime actions, citing a lack of diplomatic ties.