U.S. Secretary of State Colin Powell and visiting Japanese Foreign Minister Yoriko Kawaguchi have agreed to maintain close bilateral cooperation to effectively address Pyongyang's suspected preparations to conduct a missile test.

The two officials reportedly discussed North Korean matters on Friday in Washington, on the sidelines of a foreign ministers' meeting of G-8 member nations and Middle Eastern countries.

Japanese officials said Kawaguchi also met with South Korea's Foreign Minister, Ban Ki-moon, and agreed to keep a close watch on the Stalinist North's possible test-firing, and to seek resumption of the six-party nuclear talks at the earliest date.

Earlier this week, Pyongyang issued an aggressive threat against Japan, saying that, if pressed, it would turn the nation into a "nuclear sea of fire". This week's sabre-rattling by the North is similar to angry rhetoric it directed at Seoul back in 1994.