North Korea plans a nuclear test "in the future" to bolster its war deterrent for self-defense, according to a statement released by its foreign ministry, worsening a dispute with the United Nations over the reclusive communist country's weapons programs.

Pyongyang said it would "in the future conduct a nuclear test under the condition where safety is firmly guaranteed", though it did not state when. North Korea is believed to have a handful of warheads but is not known to have tested one before.

The US ambassador to the United Nations, John Bolton, said the US would bring up North Korea's statement for discussion Tuesday morning in a regular meeting of the UN Security Council.

"A nuclear test by North Korea would be extraordinarily serious," Bolton said in an interview with The Associated Press. "The threat is serious enough that we're certainly going to take this action in the Council this morning, by raising it."

China, North Korea's neighbor and ally, had no immediate comment. The North Korean announcement appeared to have caught the Chinese government off-guard, coming in the midst of a weeklong National Day holiday.

Japanese Foreign Minister Taro Aso called the test plans "totally unforgivable", Kyodo agency reported. The yen fell against the euro and the dollar after the announcement, which caused alarm in the region. A successful nuclear test would put pressure on Japan and South Korea to develop their own nuclear capabilities.

Six-nation talks on North Korea's nuclear program have been stalled for nearly a year, and the US has imposed financial sanctions on North Korean businesses. A nuclear test would probably be seen as a move to grab attention and force the United States into direct talks. Pyongyang accuses Washington of trying to bring down its government through a crackdown on its finances. It wants this ended before it will return to international talks to end its nuclear weapons program.

But the United States refuses to end the crackdown, which analysts say is causing Pyongyang's leadership real problems, or to hold direct talks with North Korea outside the six-country nuclear negotiations among the two Koreas, China, Japan, Russia and the United States.

The UN imposed sanctions on North Korea in July, for test-firing seven missiles  including a long-range Taepodong-2 -- believed to be capable of reaching Alaska. The missile tests also prompted South Korea to suspend aid to the North.

The statement from Pyongyang said: "The US daily increasing threat of a nuclear war and its vicious sanctions and pressure have caused a grave situation on the Korean Peninsula." It added that "under the present situation in which the US moves to isolate and stifle" North Korea, the country "can no longer remain an onlooker to the developments."

It said North Korea would never use nuclear weapons first and would "do its utmost to realize the denuclearization of the peninsula and give impetus to the world-wide nuclear disarmament and the ultimate elimination of nuclear weapons."

Analysts say North Korea has enough fissile material to make at least six to eight nuclear bombs but probably lacks the ability to make a weapon small enough to mount on a missile, Reuters reported. Western experts have said no one knows for sure whether North Korea has actually built a nuclear weapon. The country declared itself a nuclear weapons power in February 2005, without testing.