Washington ? For those who have handled them, North Korean “supernotes” are virtually indistinguishable from the $100 bills they mimic – near-perfect forgeries of the most widely circulated American bank note outside the United States.

But the fakes are more than just beautiful examples of criminal craftsmanship. They may also be the biggest hurdle to the resumption of six-nation talks meant to persuade the North to abandon its self-described nuclear weapons production program.

North Korea has refused to negotiate until the United States lifts financial restrictions imposed on a Macau-based bank and several North Korean companies for alleged counterfeiting, money laundering and other illicit activities.

With the talks deadlocked since November, some are questioning the tough U.S. stance. They argue that deepening isolation has allowed North Korea to push ahead with its weapons programs. Last month, the North ignored international warnings and test-fired seven missiles – seen by many as an attempt to put itself at the top of the world’s, and Washington’s, agenda.

U.S. officials respond that state-sponsored counterfeiting could undermine confidence in a key pillar of American strength abroad and erode the dollar’s importance as a global currency.

“A little bit of counterfeit currency of very high quality can go a very long way,” said Deputy Assistant Treasury Secretary Daniel Glaser. It can cause “people to lose their faith in the dollar, which is extremely important to the United States to maintain.”

In congressional testimony, court papers and interviews, current and former U.S. officials have described what they say is an unprecedented effort by a reclusive, communist-led government to support itself with criminal activity, including counterfeit $100 bills.

“There are some things that I thought only existed in James Bond movies and comic books before I got involved in working on North Korea’s illegal activities which I now know to be true,” said David Asher, a top State Department official on North Korea until last year.

“Holding North Korea to normal standards of behavior should not be seen as a heavy-handed pressure strategy.”

The supernotes’ trail begins in 1989, when the bills were detected in the Philippines, and stretches from Asia to Europe to both coasts of the United States.

Glaser said “numerous” North Korean diplomats have been arrested around the world carrying hundreds of thousands of dollars of counterfeit supernotes. The fakes, Asher said, “have been detected essentially on every continent in the world in the last 15 years.”

The North denies the counterfeiting charges.

But the Secret Service, which investigates counterfeiting of U.S. currency, has seized about $50 million worth of supernotes worldwide. Analysts say much more is likely in circulation.

Still, the problem the supernotes pose for the United States, officials say, is not the quantity but the high quality of the bills, which mimic the real thing right down to similar “reverse-engineered paper” and security features, such as special red and blue fibers, threads and a watermark.