Foreign Minister Nobutaka Machimura said the six nations in the talks had yet to reach a "breakthrough" as to whether Pyongyang should be allowed to pursue nuclear development for energy.

"We are not seeing a breakthrough yet on the issue of peaceful use of nuclear power. This is difficult," Machimura told reporters.

On Thursday Wu Dawei, the vice foreign minister of China, North Korea's closet ally and host of the six-nation talks, told a Japanese opposition politician in Tokyo that the nuclear talks might resume on September 2.

Asked if the talks would start on that day, Machimura said: "That is false information."

But when reporters pressed him whether the talks would come after September 2, he said: "I heard that arrangements to resume the talks sometime next week are proceeding."

When asked again whether the date of the talks was set, the minister flatly said: "No."

The six-party talks, which group the two Koreas, Russia, Japan, China and the United States, resumed in Beijing in late July after a 13-month stalemate, following North Korea's declaration in February that it already had nuclear bombs.

After nearly two weeks of sometimes heated and late-night negotiations, the talks broke off on August 7 and the key sticking point remained whether North Korea should be allowed to run nuclear programs for peaceful, energy use.

The United States has ruled out North Korea being allowed to operate light-water nuclear reactors, but South Korea has said the North should have the right to maintain a civilian nuclear program.