The communist state's pronouncement dramatically raised the stakes in the two-year-old nuclear confrontation and posed a grave challenge to President Bush (news - web sites), who started his second term with a vow to end North Korea's nuclear program through six-nation talks.

"We ... have manufactured nukes for self-defense to cope with the Bush administration's ever more undisguised policy to isolate and stifle the (North)," the North Korean Foreign Ministry said in a statement carried by the state-run Korean Central News Agency.

Previously, North Korea reportedly told U.S. negotiators in private talks that it had nuclear weapons and might test one of them. Its U.N. envoy told The Associated Press last year that the country had "weaponized" plutonium from its pool of 8,000 nuclear spent fuel rods.

But Thursday's statement was North Korea's first public acknowledgment that it has nuclear weapons. North Korea makes all important statements in the name of its Foreign Ministry spokesman and spreads them through KCNA, the isolated state's main news outlet.

North Korea's "nuclear weapons will remain (a) nuclear deterrent for self-defense under any circumstances," the ministry said. "The present reality proves that only powerful strength can protect justice and truth."

Since 2003, the United States, the two Koreas, China, Japan and Russia have held three rounds of talks in Beijing aimed at persuading the North to abandon nuclear weapons development in return for economic and diplomatic rewards. But no significant progress has been made.

A fourth round scheduled for last September was canceled when North Korea refused to attend, citing what it called a "hostile" U.S. policy.

In recent weeks, hopes had risen that North Korea might return to the six-nation talks, especially after Bush refrained from any direct criticism of North Korea when he started his second term last month.

On Thursday, North Korea said it had no intention to rejoin such talks any time soon.

"We have wanted the six-party talks but we are compelled to suspend our participation in the talks for an indefinite period till we have recognized that there is justification for us to attend the talks," the North said.

North Korea said it made the decision because "the U.S. disclosed its attempt to topple the political system in (North Korea) at any cost, threatening it with a nuclear stick."

Still, North Korea said it retained its "principled stand to solve the issue through dialogue and negotiations and its ultimate goal to denuclearize the Korean Peninsula remain unchanged."

Such a comment has widely been interpreted as North Korea's negotiating tactic to get more economic and diplomatic concessions from the United States before joining any crucial talks.

In his State of the Union address earlier this month, Bush only briefly mentioned North Korea, saying Washington was "working closely with governments in Asia to convince North Korea to abandon its nuclear ambitions."

Bush's tone was in stark contrast to his speech three years ago, when he branded North Korea part of an "axis of evil" with Iran and Iraq (news - web sites).

The nuclear crisis erupted in October 2002 when U.S. officials accused North Korea of running a secret uranium-enrichment program in violation of international treaties. Washington and its allies cut off free fuel oil shipments for the impoverished country.

North Korea retaliated by quitting the Nuclear Nonproliferation Treaty in early 2003 and restarting its plutonium-based nuclear weapons program. Its plutonium facilities had been frozen in return for oil shipments and other benefits under a 1994 deal with Washington.

The North had also claimed that it completed reprocessing 8,000 spent fuel rods previously unloaded from its 5-megawatt reactor and kept under U.N. seals under the 1994 deal. The reprocessing could yield enough plutonium for several nuclear bombs.

The North has also reloaded the 5-megawatt reactor, which can generate more spent fuel laden with plutonium.