Yeonpyeong, South Korea: South Korean marines were poised on Saturday to conduct a live-fire drill off the west coast despite a threat by the North to launch a new strike and Beijing's call for restraint from the rival states.

A US troubleshooter, Governor Bill Richardson of New Mexico, called the situation "a tinderbox" and urged the North to let the rival South conduct exercises.

Analysts were sceptical the North would carry out its threat issued on Friday, rattling financial markets in the face of a vow by the South to retaliate against any attack by Pyongyang.

The military said the exercise, planned for Dec 18-21, would go ahead off this small island 80 km from the coast, which sustained a North Korean bombardment last month.

"We will not be issuing any announcement of our plan, except reporters on the island will be notified two or three hours in advance," a marine corps officer, who spoke on condition of anonymity, said during a patrol.

Fog and brisk winds could push the drill beyond Saturday, Yonhap news agency quoted military officials as saying.

The island is normally sleepy, idyllic and home to a small crab fishing fleet that organises excursions for visitors. But it is also only a short distance from Northern Line Limit (NLL) -- the sea border declared at the end of the 1950-53 Korean War but still disputed by the North.

And many of the 1,600 residents, who live alongside 1,000 military personnel, are uneasy about the imminent prospect of a new north Korean barrage and have chosen to leave for a time -- a five-hour crossing to the mainland on often rough seas.

"I came in yesterday to check on the heating at home and the ship taking us out is being delayed," said Yoon Jing-young. "We're worried that it's because the exercises are starting today."

North Korea said on Friday it would strike with a stronger force than last month's bombardment, in which it rained 170 rounds of artillery down on Yeonpyeong, killing four people. South Korea hit back with 80 rounds.

On Saturday, the North's state media lanched a new blistering assault on the South's pledge to cooperate with the United States and retaliate in the event of a new bombardment. It suggested any such move could trigger a nuclear conflict.

"It is a suicidal move akin to digging one's own grave for the South's conservative forces to gang up with outside elements to try to harm compatriots," the official publication of the North's cabinet, Minju Joson, said in an editorial.

China, the North's main backer, issued a renewed plea on Saturday urging restraint, saying any fresh clash between the Koreas could shake regional stability. But in its hands-off stance on the rift, it singled out neither side in the call to hold back from harmful action.

"The situation on the Korean peninsula is now particularly complex and sensitive, and China is highly concerned," Chinese Foreign Ministry spokeswoman Jiang Yu said.

"China resolutely opposes, without the least ambiguity, any actions that could lead to a deterioration and escalation in the situation and wreck regional peace and stability."

Russia called on South Korea to halt plans for the drill, summoning the ambassadors from Seoul and Washington to express "extreme concern" over the exercise.

"ENORMOUS POTENTIAL FOR MISCALCULATION"

In Pyongyang, Governor Richardson of New Mexico, on a private mission to cool tensions, described the situation as "a tinderbox" and urged the North to let the South proceed with the exercises.

"There's enormous potential for miscalculation," he said in a telephone interview with CNN. "I'm urging (the North) extreme restraint ... Let's cool things down."

The US State Department underscored the US stance that South Korea had every right to conduct the exercises, but indicated that it, too, was worried.

"We are absolutely concerned about the current trajectory," State Department spokesman P.J. Crowley said, adding that Pyongyang was responsible for raising the tensions.

"We trust that South Korea will be very cautious in terms of what it does, but that said, let's put the responsibility squarely where it lies," he said.

North Korea is seeking the resumption of six-party talks with the United States, China, South Korea, Japan and Russia aimed at persuading Pyongyang to abandon its nuclear programme.

It wants the talks to resume without preconditions, something Washington and South Korea have ruled out because they do not want to reward Pyongyang for hostile actions.

Analysts say the North uses the threat of attacks and even nuclear conflict to win concessions such as food and economic aid at talks over its nuclear stockpile.

At the same time as the poor, reclusive country is pushing for aid, the North is also in the throes of a potential leadership succession as ailing leader Kim Jong-il grooms his youngest son, Kim Jong-un, as the next ruler.