"We're continuing to expect the North Koreans to take this issue seriously because it is a major issue for Japan and it's a major issue for the United States," she said.

On Wednesday George Bush, the US president, reportedly gave assurances to Yasuo Fukuda, Japan's prime minister, that he "would not forget the abduction issue".

The abduction of its citizens remains a sensitive issue in Japan [EPA]
According to Japan's foreign ministry Fukuda asked Bush for continued US support in resolving the issue, saying it was also important to press ahead with stalled six-nation talks on the North Korean denuclearisation.

Tokyo has long pushed for the resolution of the abduction of Japanese nationals in the 1970s and 80s as a condition for providing aid and improved relations to North Korea.

North Korea has admitted to kidnapping 13 Japanese citizens, and has allowed five to return home.

It says the other eight died of natural causes, an explanation that Japan has refused to accept.

The abductees were apparently abducted as part of a bizarre plot to train North Korean spies in Japanese language and customs.