The State Department, echoing similar comments from the Japanese government, said Japan "must and will" continue to participate in the talks because of Tokyo's vital interests in seeing a resolution to the standoff.

"We agree with the Japanese in rejecting the North Korean attempt to exclude Japanese participation in the multi-party talks," spokesman Richard Boucher said.

"Japan is a neighbor of North and South Korea and has vital interests at stake in the nuclear issue and in other areas as well," he told reporters.

"North Korean actions, particularly with regard to missiles and their pursuit of nuclear weapons have raised the concern of its neighbors, including Japan, and North Korea must deal with those concerns," Boucher said.

"Japan clearly must and will continue to be a participant in the six-party talks in order to achieve a diplomatic solution to North Korea's nuclear programs," he said.

Earlier Tuesday, North Korea, which has raised the stakes in the crisis by claiming to be making atomic bombs and reprocessing spent nuclear fuel rods, threw up new obstacles to any resumption in the Chinese-hosted talks by demanding Japan's exclusion.

The six-party format includes China, Japan, North and South Korea, the United States and Russia.

But Pyongyang said it "would not allow Japan to participate in any form of negotiations for the settlement of the nuclear issue in the future."

North Korea said Tokyo had aligned itself with Washington on the nuclear crisis and for its crackdown on a pro-North Korean group in Japan known as Chongryon.

It also faulted the Japanese for using the talks to raise the issue of Japanese citizens abducted by North Korea during the 1970s and 1980s.

Japan rejected the North Korean move with a foreign ministry spokesman saying that Tokoyo had "no intention of accepting it at all."

The statement, on the North's official Korean Central News Agency (KCNA), cast doubt on plans for a new round of talks, which South Korean President Roh Moo-Hyun has said were expected to take place soon.

A first round of talks in Beijing in August ended inconclusively, and the North Koreans expressed no interest in continuing the dialogue without concessions from the United States, which Washington refused.

Pyongyang has held out for a non-aggression pact as a first step before responding to Washington's demand for a complete and verifiable dismantling of its nuclear weapons drive.

It said Tuesday it would step up its nuclear weapons drive and dismissed an offer tendered by the top US envoy for Asia, James Kelly, of a non-binding written security guarantee as "a blank sheet of paper" without any legal guarantees.

North Korea has accused Washington of planning a nuclear strike against it, ignoring frequent denials from US officials.

WAR.WIRE