"We will neither treat Japan as a party to the talks nor deal with it even if it impudently appears in the conference room," a North Korean Foreign Ministry spokesman was quoted as saying by Pyongyang's official Korean Central News Agency.
Japan "has not done anything to fulfill its commitment, and is still refusing to do so," the spokesman said.
The negotiations - which have until now brought together the two Koreas, China, Russia, the U.S. and Japan - are expected to resume in Beijing on Monday, although the date has not been officially confirmed.
North Korea has made several calls in the past for Japan to be excluded from the talks process.
The spokesman accused Japan of seeking to scupper the negotiations and seek a pretext for its militarization.
"Such a country has neither justification nor qualifications to participate in the talks. On the contrary, it only puts a hurdle in the way of achieving the common goal," he said.
Japan has refused to provide its share of the one million tons of fuel aid pledged to the reclusive communist state under a February 2007 deal, demanding that Pyongyang first disclose all information on Japanese nationals abducted by the North during the 1970s and 1980s.
Under the six-party deal, the North pledged to dismantle its plutonium-producing Yongbyon reactor and provide full information on its nuclear program.