(CNN) A day after North Korea said it will conduct a nuclear test, world powers called for restraint.
The United Nations Security Council was due to discuss the issue later Wednesday amid growing fears over Pyongyang's military capabilities, reports Trend.
U.S. Ambassador John Bolton has already urged members to engage in "preventive diplomacy" and "come up not just with a knee jerk reaction."
China, North Korea's closest political ally, warned its neighbor against exacerbating tensions already simmering over the hermetic Stalinist country's nuclear ambitions.
"We hope that the DPRK (Democratic People's Republic of Korea's -- the north's official name) will keep calm and restrained on the nuclear test issue," Foreign Ministry spokesman Liu Jianchao said in a statement reported by Chinese state media.
Japan's new Prime Minister, Shinzo Abe, took a tougher stand, as did South Korea's President Roh Moo-hyun.
"If North Korea were to conduct the nuclear test, it would be absolutely unacceptable," Abe said.
Roh called for a "cool-headed and stern" response to North Korea's threat, his office said. (Full story)
North Korea on Tuesday announced its plan to carry out a nuclear test, citing American belligerence. It did not give a time or location.
Although Pyongyang has previously claimed to possess nuclear weapons capabilities, such a test would be the first conclusive proof.
Announcing the nuclear test on state media, North Korea said its aim was peaceful.
"The field of scientific research of the DPRK will in the future conduct a nuclear test under the condition where safety is firmly guaranteed," it said. (Watch why North Korea may want to test a nuclear bomb -- 3:37)
Six-party talks on North Korea's nuclear program have been stalled since November last year. Pyongyang wants bilateral engagement with the United States before the talks resume and it wants Washington to ease up on economic pressures.
The talks involve China, Japan, Koreas, Russia and the United States.
Tensions over the North's nuclear ambitions began to rise in late 2002 when Washington accused Pyongyang of running a clandestine atomic bomb program in violation of its pledge not to do so. Pyongyang denies the claim.
In mid-July, the North test fired missiles capable of carrying a nuclear warhead, prompting the United Nations to pass Resolution 1695, condemning the tests and demanding it suspend further missile launches.
U.S. ally Australia, which has diplomatic relations with North Korea, called the North Korean ambassador in Canberra Wednesday to register its "grave concern" over the latest development.
France's U.N. Ambassador Jean-Marc de La Sabliere said he thought it was important "that the council reacts and reacts swiftly and with a strong message."
"We also have to define a strategy and discuss how the council has to react, but first we must issue a statement," he said.
U.N. Secretary-General Kofi Annan urged North Korea's leadership "to exercise utmost restraint," observe the current moratorium on nuclear testing, and return to the six-party talks, U.N. spokesman Stephane Dujarric said.