The United States refused Wednesday to withdraw financial sanctions on what it called North Korea's "criminal regime," accusing the government of arms-dealing, drug sales, money-laundering and counterfeiting.

"It's up to North Korea to end the behavior that led to those sanctions," U.S. Ambassador to South Korea Alexander Vershbow told the National Press Club in Seoul. "This is a criminal regime and we can't somehow remove our sanctions as a political gesture."

His description of the North provoked strong criticism from a top South Korean official.

"It's not desirable to publicly characterize the other side," Son Min-soon, South Korea's chief negotiator at six-party talks over the North's nuclear ambitions, told The Associated Press in Kuala Lumpur, Malaysia. "If North Korea makes a similar characterization, would that be good?"

Vershbow's tough talk came one day after North Korea threatened to boycott the six-nation talks on eliminating its nuclear weapons programs unless Washington lifts sanctions imposed in October.

Officials in the South, which has been pursuing a detente of sorts with the North since the two countries' leaders held their first summit in 2000, have in recent years avoided strongly worded criticisms of the North.

The United States imposed sanctions targeting eight North Korean companies it said acted as fronts for the proliferation of weapons of mass destruction. North Korea vehemently denies the allegations.

The North engaged in the "export of dangerous military technology, narcotics trafficking, money laundering, the counterfeiting of U.S. currency and many other illicit activities," Vershbow said.

Vershbow, who assumed his post in October, refused to characterize North Korean leader Kim Jong Il but said the state he runs is "a very repressive regime" that continues to possess "concentration camps for political prisoners."

Regarding the counterfeiting of other countries' money, Vershbow remarked that "according to one observer, it's the first regime that's done that since Adolf Hitler." Vershbow didn't identify his source.

The North's official Rodong Sinmun newspaper made the threat to suspend participation in the six-party talks in a commentary carried Tuesday by the official Korean Central News Agency.

"It is impossible to resume the six-party talks under such provocative sanctions applied by the U.S.," the commentary said.

The talks, launched in 2003, involve China, the United States, the two Koreas, Japan and Russia. Their fifth and latest session recessed in November with no signs of progress on persuading the North to disarm. The parties agreed at the end of the fifth session to meet again at an early, though unspecified, date.

North Korea says Washington agreed in the last round of talks in Beijing to hold negotiations on the sanctions. The U.S. denies such an offer.

The Rodong Sinmun commentary also called on the U.S. to respect the North and not take any actions that would impede the progress of nuclear talks. An earlier version called the sanctions a U.S. conspiracy to win concessions from the North on the nuclear issue.

"Our enforcement of U.S. law should not be used to hold up the six-party talks," Vershbow said Wednesday.

"North Korea has tremendous economic and social problems, none of which will be solved by the pursuit of nuclear weapons," he said.

The North and South, which fought the 1950-53 Korean War and remain technically in a state of conflict as a peace treaty was never concluded, are divided by a heavily armed border, the world's last Cold War frontier.