The Japanese foreign minister on Monday rejected China's proposal of emergency six-party talks on North Korea aimed at defusing the crisis on the divided peninsula, the Wall Street Journal said.

Seiji Maehara told the newspaper there would be no point in restarting stalled discussions between the isolated North and five other nations including Japan unless they could make real progress.

"It's unacceptable for us to hold six-party talks only because North Korea has gone amok," the minister said.

"We must first see some kind of sincere effort from North Korea, on its uranium enrichment program and the latest incident."

Prime Minister Naoto Kan has yet to formally reject the proposal, having told reporters earlier Monday: "We want to respond to (the proposal) cautiously while consulting with the United States and South Korea."

The details of a meeting between Maehara, South Korea's Foreign Affairs and Trade Minister Kim Sung Hwan, and US Secretary of State Hillary Clinton, were under discussion Tuesday, according to Japan's Kyodo news.

The meeting has been pencilled in for December 6 in Washington, the report said.

Tensions rose sky-high last week after the North shelled a South Korean border island, killing four people and wounding 18 in the first bombardment of a civilian area in the South since the Korean war.

China, Pyongyang's sole major ally, on Sunday proposed "emergency consultations" in Beijing early next month among chief envoys to the stalled six-nation talks on Pyongyang's nuclear disarmament.

Its top envoy on North Korea, Wu Dawei, stressed that the proposal did not constitute a formal resumption of the negotiations, but he said he hoped they would lead to such a resumption soon.

South Korea, the United States and Russia are also involved in the six-party talks but Washington has urged North Korea to stop what it describes as provocative behaviour before they can resume.

State Department spokesman Philip Crowley said Sunday that Washington would "continue to consult with others, including China, on a future course".

South Korea, which is pressing Beijing to be more even-handed in the standoff, has also reacted cautiously to the talks proposal, saying it wanted to see "tangible actions" from its neighbour on denuclearisation.

Shortly before the North's deadly attack on the South Korean island of Yeonpyeong on November 23, it sparked alarm by showing an American scientist a new uranium enrichment facility that he said could be used for nuclear weapons.

The US and South Korea on Monday staged the second day of their biggest-ever naval exercise in a show of strength against North Korea's regime, which has also tested nuclear bombs and is blamed for sinking a South Korean warship in March.

Far to the south of the disputed border between North and South, the US and South Korean fleets staged an intensive live-fire exercise involving multiple aircraft from the US carrier George Washington.

Eleven ships from the two navies plus aircraft and more than 7,000 personnel are taking part in the four-day drill.

North Korea said the exercise brings the peninsula to the brink of war, and the drill has also riled China, which sees the Yellow Sea as its backyard.

Stanford University professor Siegfried Hecker was taken to visit North Korea's new and previously unknown uranium enrichment plant this month and said it was equipped with at least 1,000 centrifuges.

Pyongyang's latest moves could be to generate much-needed electricity, he said in a report on the plant at the Yongbyon nuclear complex.

"Yet, the military potential of uranium enrichment technology is serious."