North Korea's sole major ally China yesterday urged "all relevant parties" to show restraint after Pyongyang said it planned to carry out a third nuclear test and more rocket launches aimed at the US.
"All relevant parties should refrain from action that might escalate the situation in the region," Foreign Ministry spokesman Hong Lei said in Beijing.
China hoped they would "stay calm, be discreet in words and deeds and look at the long-term interests, and push for the resumption of the six-party talks," he said, referring to long-stalled negotiations over the North's nuclear programme.
The comments came after the North hurled fresh invective at its US-led foes in a statement from its National Defence Commission, without specifying when the atomic test - part of an "upcoming all-out action" - might be carried out.
"We do not hide that the various satellites and long-range rockets we will continue to launch, as well as the high-level nuclear test we will proceed with, are aimed at our arch-enemy the United States," it said.
"Settling accounts with the US needs to be done with force, not with words," it added in the statement carried by the official Korean Central News Agency.
It did not elaborate on the meaning of "high-level".
Some experts have predicted that the North's next test might be of a uranium bomb, rather than the plutonium devices it detonated on two previous occasions. Such a development would indicate it had mastered the sophisticated technology needed to produce highly enriched uranium (HEU).
"The statement reads like typical North Korean brinkmanship and we can't definitely say a test is imminent," said Kim Yong-hyun, professor of North Korea studies at Dongguk University.
"But it's highly possible that it will use HEU for the test when it happens."
The North's threat coincided with a visit to Seoul by the US special envoy on North Korea, Glyn Davies, who urged Pyongyang not to go ahead with a third test.
"Whether North Korea tests or not, it's up to North Korea," Davies said after meeting his South Korean counterpart and speaking shortly before the North's statement. "We hope they don't do it, we call on them not to do it. It would be a mistake and a missed opportunity if they were to do it."
South Korea's Foreign Ministry spokesman voiced regret over the test threat and urged Pyongyang to heed the warnings against further provocative acts.
Much of the North's statement was devoted to condemning Tuesday's announcement by the UN Security Council of expanded sanctions against Pyongyang in response to its long-range rocket launch last month.
"We absolutely reject all the illegal and outlawed resolutions adopted by the Security Council," the commission said.
Tuesday's resolution, proposed by the United States, was adopted unanimously by the 15-nation council, including China.