North Korean envoy Kim Kye-Gwan met his US counterpart in Singapore
North Korea says it will not recognise Japan as a member of six-nation nuclear disarmament talks due to resume in Beijing on Monday.
The move follows Japan's refusal to provide aid to North Korea under a disarmament-for-aid pact.
Tokyo and Pyongyang are in dispute over North Korea's kidnapping of Japanese citizens in the 1970s and 1980s.
Correspondents say it is not yet clear how North Korea's declaration will affect the meeting.
Speaking ahead of the North's announcement, US envoy Christopher Hill said: "I am sure the negotiations will be as usual: they will be difficult."
Mr Hill was due to arrive in the South Korean capital Seoul for consultations on Saturday, before flying on to Beijing.
North Korea's rejection of Japanese involvement in the talks came in a statement from the foreign ministry carried by the official Korean Central News Agency.
Snatched in the '70s and '80s
Used as cultural trainers for North Korean spies
Five allowed home in 2002
Five children now freed from North Korea
Eight said to be dead, others missing
"We will neither treat Japan as a party to the talks nor deal with it even if it impudently appears in the conference room, lost to shame," it said.
Japan "has neither justification nor qualification to participate in the talks. On the contrary, it only lays a hurdle in the way of achieving the common goal".
The statement said that Tokyo's aim was to block denuclearisation to give it a pretext to boost its military power.
North Korea agreed to disable its plutonium-producing Yongbyon nuclear complex in a 2007 six-party pact with the US, South Korea, China, Russia and Japan.
In return, it was to get one million tons of fuel oil or energy aid of the same value. About half that amount has so far been delivered.
However, Japan has refused to provide its share of energy aid until the question of its abducted citizens is resolved.
In 2002, North Korea acknowledged kidnapping 13 Japanese citizens and allowed five to return home, saying that the remaining eight had died.
But Japan is demanding proof of the deaths and an inquiry into other suspected kidnapping cases.
The two countries struck a deal in June under which North Korea pledged to finally resolve the abductions of Japanese citizens, but no major progress has been made since then.
Separately, the US removed the North from a terrorism blacklist in October, as agreed under the pact.
In return, North Korea agreed to provide full access to its nuclear programme.
However, analysts say the negotiations have been fraught with disagreements and have previously broken down over different interpretations over what is required.
Mr Hill and his North Korean counterpart, Kim Kye-gwan, held two days of preparatory talks in Singapore this week ahead of the negotiations in Beijing.
Mr Hill visited Pyongyang in early October to try to save the deal but correspondents say that the two sides now differ on what was agreed at that time.
North Korea insists it never agreed to samples of atomic material being taken away for examination.
The US asserts that the North did consent to the procedure. Mr Hill said they had failed to reach an agreement in Singapore but indicated there would be more talks in Beijing on the issue.