Updated

In a presidential race dominated by national security, what some see as the world's biggest nuclear danger — North Korea (search) — is only now emerging as a hot political topic.

It's a difficult subject for Republicans and Democrats alike. North Korea doesn't dominate the news the way Iraq does, making it an unlikely issue for winning votes. Moreover, both parties are vulnerable to criticism on their handling of the North Korean threat.

President Bush (search) has said that he will not tolerate nuclear weapons (search) in North Korea. Yet North Korea, long believed to have possessed one or two nuclear weapons, has restarted its weapons program and could soon have several more, if it doesn't have them already. Multinational negotiations appear to have produced little.

Republicans argue actions of the Clinton administration led to the current standoff. They say a 1994 agreement for North Korea to freeze its nuclear program in exchange for food and energy assistance lacked safeguards to prevent cheating. That allowed North Korea to develop a secret uranium-based weapons program, they say, even while the older plutonium program was stopped as promised.

Although North Korea hasn't been at the forefront for most of his campaign, Democratic nominee John Kerry (search) has accused Bush repeatedly of being so fixated on Iraq that he ignored the danger posed by the Kim Jong Il's government in Korea.

Kerry stepped up the criticisms after an explosion Thursday that raised fears North Korea had conducted a nuclear test. The North Koreans say the explosion was the result of the demolition of a mountain for a hydroelectric project. U.S. officials say they do not believe it was a nuclear blast, accidental or otherwise.

"The mere fact that we are even contemplating a nuclear weapons test by North Korea highlights a massive national security failure by President Bush," Kerry said Sunday.

In a telephone call to The New York Times, Kerry accused the administration of letting "a nuclear nightmare" develop in North Korea.

Bush spokesman Scott McClellan accused Kerry of wanting to return to "the failed Clinton administration policy" on North Korea.

"That failed policy let North Korea dupe the United States. It would be the wrong approach to go down that road again," he said Monday aboard Air Force One en route to a Bush campaign stop.

North Korea is a rigid dictatorship, frequently accused of human rights abuses, and is on the State Department's list of nations that sponsor international terror. Bush included it as part of his "axis of evil" with Saddam Hussein's Iraq and Iran, which also is suspected of developing nuclear weapons.

The United States accused North Korea two years ago of having a clandestine uranium enrichment program. North Korea maintains uranium mines producing high quality uranium ore, necessary for either a uranium-based or plutonium-based bomb. Refining uranium for uranium-based bombs is easier and less-complicated than for more powerful plutonium bombs. U.S. officials say North Korea admitted to the clandestine program; North Korea denies it.

The Bush administration suspended fuel shipments promised under the 1994 agreement. North Korea expelled international monitors, withdrew from the Nuclear Nonproliferation Treaty and restarted its plutonium reprocessing facility. It claims to have reprocessed 8,000 spent nuclear fuel rods, which can yield enough plutonium for several bombs.

Bush has stressed that it will work with the negotiating partners — South Korea, Japan, China and Russia — toward a verifiable dismantling of North Korea's nuclear weapons programs. Administration officials hope North Korea will follow the model of Libya, which has begun improving relations with the United States after agreeing to end its nuclear weapons program.

Three rounds of multinational negotiations have been held so far. Another round was planned for this month, though no date has been set. Some analysts expect no progress until after the November presidential election, contending North Korea hopes negotiations would be easier under a Kerry administration.

Kerry has said he would be willing to negotiate directly with North Korea, alongside the six-nation talks.

As the North Korean threat has grown, Bush has pressed for rapidly building a missile defense system. Kerry is skeptical that untested missile defense systems could offer protection soon and favors diverting some missile defense money to other security programs. Kerry has also criticized Bush's plans to withdraw about a third of the 37,000 U.S. troops in South Korea as part of a worldwide realignment of forces.

Charles Pritchard, a former State Department official who was part of an unofficial delegation to North Korea in January, said the North Korean problem "will become more and more difficult as time goes by."

"Whoever is president after the next election will have to pick up the pieces and move forward because you will have a situation in which North Korea may very well be a de facto nuclear weapons state and changing the dynamics in northeastern Asia," he said.