Some analysts consider the threat as part of the North's strategy to grab Washington's attention and gain leverage in future talks with the United States because it did not provide any specific date for a nuclear test.

The North, in the Foreign Ministry statement, has also promised to make the Korean peninsula free of nuclear weapons and refrain from transferring nuclear materials, indicating its hope of last-minute negotiations to end the nuclear standoff.

"The announcement seems aimed at raising stakes in the nuclear standoff for direct talks with the United States," said Koh Yu-hwan, a North Korea specialist at Dongguk University in Seoul. The North is seeking to bluff the United States into looking afresh at stalled negotiations over Pyongyang's nuclear drive and U.S.-led financial sanctions, he said.

Kim Young-soo, a professor at Sogang University, also ruled out the North would go through with a nuclear test that threatens "grave consequences."

The United States has considered a nuclear test, a key step in the manufacture of atomic bombs, as the "red line" that could warrant the use of force. Some hard-liners in Washington and Tokyo have already called for a pre-emptive attack on the North's nuclear site if there were an imminent threat.

Kim said the nuclear test threat is the last card the North has in order to win direct talks with Washington.

North Korea has taken a series of steps to raise the stake. It claimed in February last year that it possessed nuclear weapons and declared itself a nuclear power. It also announced claims to have extracted more weapons-grade plutonium to make additional atomic weapons.

Ratcheting up tensions, North Korea test fired a set of missiles on July 5, including a long-range ballistic missile. The Taepodong-2 missile, equipped with a nuclear warhead, may be capable of reaching the continental United States.

But the set of threats failed to grab attention from the United States, whose focus was primarily focused on Iran's nuclear issue and the Middle East crisis. The missile launches have only led to U.S.-led financial sanctions which are believed to chock off Pyongyang's cash flow.

Analysts said the North's announcement of its nuclear test is also aimed at influencing U.S. mid-term elections slated for November.

The North's earlier brinkmanship succeeded in pressing the United States to hold direct talks after it launched a long-range Taepodong-1 ballistic missile and pulled out of the non-proliferation treaty. Through the bilateral talks, Pyongyang has won concessions from the United States highlighted by the 1994 Agreed Framework.

"With the nuclear test threat, the North wants to press the United States to ease its financial sanctions," said Kim Kun-shik, a North Korea expert at Kyungnam University in Seoul.

However, quite a few other analysts expect the North to go ahead with a plan to test a nuclear weapon in the face of tougher sanctions.

"With the (Tuesday) announcement, the North is bound to conduct a nuclear test any time," said Paik Hak-soon, a North Korea expert at Seoul's private Sejong Institute. "We cannot rule out a nuclear test."

A nuclear bomb test by North Korea would prove its nuclear capability for the first time, a development that would create a catastrophic ripple effect in Northeast Asia.

Kim Tae-woo, a nuclear strategy expert at Seoul's government-run Korea Institute for Defense Analysis, said the North has both capabilities and motivations to conduct a nuclear test. "A nuclear test in the North now depends on the supreme leader's final choice," he said.

Some analysts predict a nuclear test to occur on Oct. 10, when the North marks the founding anniversary of the ruling Workers' Party, or ahead of the U.S. mid-term election in November.

South Korea's top security policymaker, Unification Minister Lee Jong-seok, also said North Korea is "highly likely" to go ahead with its plans to test a nuclear weapon if South Korea and the United States fail to induce the North back to the negotiating table.

"The government believes the (North Korean) statement is aimed at pressuring the United States to change its stance" toward the North, Lee told the National Assembly on Wednesday.

"However, the government believes there is a high possibility of a nuclear test if the efforts to resume the six-party talks end in failure," he said.

"There is a possibility that North Korea may take the action ahead of the November mid-term election in the United States unless Washington takes clear steps toward direct negotiations," Lee said.

The Foreign Ministry said it intends to issue a strong warning to its northern neighbor. "It is necessary to send a grave warning to North Korea so that it does not misjudge the current situation and conduct a nuclear test," it said.

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