U.S. Ambassador to Seoul Alexander Vershbow says Washington possesses forensic evidence that North Korea counterfeited U.S. bills.

In a Friday lecture in Seoul, he also said that to resolve the problem, Pyongyang must show verifiable action that it has stopped the counterfeiting.

The U.S. envoy said Washington, based on forensic science and data analysis, believes the North produced fake 100 dollar "super notes", adding that his government would share the intelligence with South Korea and may publicly disclose the information.

He said persuading the North to halt illegal activities is most important and urged the communist state to pledge to halt the activities.

Vershbow added that his country will unconditionally participate in the six-way nuclear talks when the dialogue resumes next month, but reiterated that the U.S. will not accept North Korea's demand for the provision of a light water reactor before its nuclear dismantlement.