Regardless of whether North Korea launched a missile or a satellite late last month, the action was a threat to Northeast Asia because it proved that North Korea has the technological ability to develop a medium-range missile, South Korean Ambassador to Japan, Kim Suk Kyu, said Wednesday.

"North Korea's ability to launch a two-stage (rocket) is a grave concern, regardless of whether it launched a missile or a satellite," Kim told a press conference at the Japan National Press Club.

Kim said that North Korea's action was a threat not only for Japan and South Korea but also for all of Northeast Asia. Coordination between Seoul and Tokyo is essential to deal with the issue, said Kim, who assumed the ambassadorial post in June.

The United States said Monday that its experts have concluded that North Korea's action was a failed attempt to put a very small satellite into orbit.

Kim, meanwhile, stressed the importance of President Kim Dae Jung's policy of seeking reconciliation with North Korea, arguing that Pyongyang's opening up to the international community is in the long-term interest of both neighboring countries and the entire world.

Kim said the light-water nuclear reactor project under the Korean Peninsula Energy Development Organization is important because it is the only window through which inward-looking Pyongyang can hold dialogue with the international community.