Yeonpyeong: South Korea said on Sunday bad weather was delaying the start of a live-fire exercise that prompted North Korean threats of war, adding that it had no plans to scrap the drills despite international calls for restraint.

The U.N. Security Council is expected to convene an emergency session on Sunday on the escalating tension between North and South Korea in the hope of issuing some kind of statement to help ease the tension in the region.

North Korea has called the artillery fire drill by the South, on Yeonpyeong island which was attacked last month, a suicidal war move that would trigger a full-out conflict on the Korean peninsula and said it would strike back in self-defense.

Analysts were sceptical the North would carry out the threat it issued on Friday, which rattled financial markets, but it added to the already tense situation in the peninsula which has been described as "extremely precarious" and a "tinderbox" by U.S. and Chinese officials.

The North will likely respond by holding a live-fire drill on its side of the tensely guarded sea border, if the South went ahead with its exercise, analysts said.

Weather conditions worsened on the normally sleepy, idyllic island of fishermen, forcing the military to push back a planned one-day live-fire drill past the weekend. It had been scheduled for some time between Dec. 18 and 21.

"There is no plan to cancel the exercise. The factor we're looking at is the weather condition," a Defence Ministry official said on the condition of anonymity.

South Korean marines plan to test artillery firing from the island targeting its territorial waters to its southwest, the same type of exercise that North Korea last month called an attack and returned fire, killing four people.

U.S. troubleshooter Bill Richardson, the governor of New Mexico who is on a private mission to Pyongyang, said he had made some progress in his discussions with officials there.

He told CNN he did not get a firm answer on whether North Korea would physically strike the South again, but added: "It's still very tense out there"

"They said there would be a response, but at the same time they hope a U.N. Security Council resolution would tamp down the situation. It was very clear they were very upset by the potential exercise," Richardson told CNN from Pyongyang.

China, the main backer of the isolated North Korea, again urged the rival Koreas to open talks and avoid steps that could inflame tensions on the peninsula, extending its effort to contain a confrontation on its doorstep.

"China resolutely opposes any actions that could inflame tensions and exacerbate the situation, and asks that both sides of the peninsula exercise calm and restraint and open up dialogue and contacts," Foreign Minister Yang Jiechi said on Sunday.

Yang spoke to his Russian counterpart Sergei Lavrov but did not blame either the North or the South directly, maintaining China's policy of avoiding becoming embroiled in the bitter rift between its neighbours.

Russia also said the two Koreas must begin dialogue to try to resolve all issues of dispute. Ambassador to the United Nations Vitaly Churkin said the Security Council will meet on Sunday in the hope of delivering a message to the two rival states.

"We are seriously concerned about possible further escalation of tensions on the Korean peninsula," Vitaly Churkin said, adding that the situation there "directly affects the national security interests of the Russian Federation," he told reporters at the Russian U.N. mission in New York.

The U.S. State Department said last week that South Korea had every right to conduct the exercises, but indicated that it, too, was worried.

"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," a State Department spokesman said.

North Korea continued with blistering assault on the South and the United States on Saturday, blaming Seoul for conspiring with Washington to bring hostility against a neighbour.

The North's foreign ministry spokesman said in a statement: "We will be sure to settle scores with the U.S. for the extreme situation on the Korean peninsula." He added: "Our military does not speak empty words."