Prime Minister Junichiro Koizumi on Friday urged North Korea to immediately reverse its decision to pull out of the nuclear Nonproliferation Treaty.

"It is extremely regrettable that North Korea has declared it will withdraw from the Nonproliferation Treaty," Koizumi, who is currently on an official visit to Russia, said in a statement, adding that Japan has "grave concerns" over the development.

Chief Cabinet Secretary Yasuo Fukuda said Japan will consult closely with the United States and South Korea on what steps to take after thoroughly analyzing North Korea's statement announced earlier in the day.

Pyongyang's bold declaration came just after Washington said it was willing to talk to North Korea following a high-level meeting between the U.S., Japan and South Korea in Washington on Wednesday.

While the latest move can be seen as further brinkmanship by North Korea, Fukuda said it would not hamper Japan's efforts to hold a dialogue with the North.

"It's not (the case) that we cannot have negotiations with North Korea because of (the announcement)," Fukuda said. "We will try to resolve the issue through dialogue."

Fukuda stopped short of saying that the Korean Peninsula Energy Development Organization -- an international consortium to build nuclear reactors in North Korea in exchange for Pyongyang's freeze on nuclear development -- had failed. He said Japan will discuss the matter with the U.S. and South Korea.

"It's easy if we say it, but we need to talk with relevant countries," the top spokesman said. "What we should do now is call on North Korea to stop the action and respond to our calls for talks."