A top US disarmament official has urged North Korea to follow Libya's example and give up its weapons of mass destruction.
John Bolton is one of North Korea's harshest critics
John Bolton, a leading US expert on North Korea, said Washington was not interested in a temporary freeze of the North's nuclear facilities.
He said that path had already been tried once before, and the US would not be fooled again.
The US and Pyongyang have been engaged in a 20-month standoff over the issue.
Mr Bolton's comments, in a lecture to Seoul's Yonsei University, came ahead of the arrival in South Korea of Japanese Prime Minister Junichiro Koizumi.
Mr Koizumi and South Korean President Roh Moo-hyun held 90-minute talks on the holiday island of Jeju, where they pledged to co-operate to extend aid to the communist North once it had dismantled its nuclear programmes.
Mr Bolton has in the past launched scathing attacks on North Korea, on one occasion calling it a "hellish nightmare". Pyongyang, in return, has labelled him "human scum".
But this time the under-secretary of state outlined a way for North Korea to escape its pariah status.
"Let there be no doubt: The case of Libya has shown concretely the benefits that can flow when leaders of isolated regimes make the strategic choice to invest in their countries' future, and not in weapons of mass destruction," Mr Bolton said in a lecture at Seoul's Yonsei University.
He said ongoing negotiations were not making much progress because North Korea refused to admit to the full extent of its nuclear facilities.
Pyongyang denies US allegations that it has an enriched uranium programme, in addition to a plutonium one.
It has offered to freeze the plutonium programme, but the US says a freeze is not enough and all facilities must be permanently dismantled.
An agreement in 1994 gave the North energy aid in return for a nuclear freeze, but that pact collapsed in 2002 when the US said Pyongyang admitted to a secret uranium programme. Since then it has also restarted its plutonium programme.
"We have a saying: 'Fool me once, shame on you, fool me twice, shame on me.' We will not be fooled again.
"Our experience with Libya shows that a freeze is unnecessary, and moreover, would simply delay the time when the people of North Korea could reap the benefits of rejoining the international community," Mr Bolton said.
At six-party talks last month, the Bush administration proposed to give the North fuel aid and other benefits in return for a commitment to dismantle all its nuclear facilities.
But Mr Bolton said North Korea should not be rewarded "merely for coming back into compliance with their past obligations".
"It is not only anathema to our values - it is a bad policy," he said.
BREAKING THE DEADLOCK?
US reportedly ready to agree to fuel aid and 'provisional guarantee' not to attack
Talks on lifting US sanctions also on offer
In return, North must seal nuclear facilities within 3 months
Fuel aid and talks will continue if North then dismantles facilities
The BBC's correspondent in Seoul, Charles Scanlon, says there was little in Mr Bolton's speech to comfort the North Koreans.
They want a nuclear deal on their own terms, and are unlikely to be attracted by a Libyan style solution with only a vague promise of international goodwill, our correspondent says.
And Mr Bolton's demands did not end with an abolishment of the North's nuclear activities - he also wants Pyongyang to reduce its conventional military threat and improve human rights.
He warned of tougher international enforcement measures if North Korean leader Kim Jong-Il failed to comply with American demands.
The US is trying to co-ordinate a regional position on Pyongyang.
Analysts say Mr Koizumi will have been interested in trying to ensure that Seoul's softer line on its neighbour does not deviate too far from Washington's tougher stance.
Mr Roh said after his talks with Mr Koizumi that the two countries would co-operate to help North, once Pyongyang comes out from the diplomatic cold.
"My country will carry out detailed and comprehensive economic co-operation projects with the North, and Japan will actively pursue diplomatic relations and economic co-operation with the North," he told a news conference.
A further round of six-party talks on the nuclear issue are expected before the end of September.