A visitor to the site asked Alexander Vershbow about an earlier statement calling Pyongyang a "criminal regime."
In response, Vershbow praised South Korea's efforts to relieve suffering in North Korea, but said the country's policy should be geared to encouraging the regime to become more open. He made his comments on the Cafe USA site, the Korea Times reported.
"I think all South Koreans should be worried about a regime that threatens its own people so badly, that wastes its scarce resources on nuclear weapons, and that engages in counterfeiting, drug trafficking, money laundering and the export of dangerous military technologies in order to survive," Vershbow said.
North Korea sometimes refers to Vershbow as the "governor general" of South Korea.