The US has said it expects North Korea to fully account for its uranium enrichment programme for nuclear weapons under a deal to begin scrapping its atomic arms.
The US Deputy Secretary of State, John Negroponte, who is on a visit to Seoul, said it was in North Korea's interest to comply with the agreement reached last month.
Under a six-country deal reached on 13 February, Pyongyang has agreed to begin talks within two months and to produce a comprehensive list of its nuclear activities, including enrichment.
Mr Negroponte said the US expected that this would be addressed when North Korea made its declaration of nuclear facilities.
He said the agreement reached last month was a good first step.
It calls for North Korea to shut down its main nuclear reactor and source of weapons-grade plutonium in exchange for energy aid.
Mr Negroponte said US officials could make a rare trip to Pyongyang as part of the negotiating process.
