US Secretary of State Condoleezza Rice pressed North Korea on Saturday to give up all its atomic weaponry after the communist state delivered a nuclear declaration and demolished part of its reactor.
"In the next phase we do have to move on abandonment," she told a press conference in the South Korean capital, referring to a six-nation nuclear disarmament deal.
Rice said the declaration which the North delivered on Thursday to talks host China included references to US concerns about a suspected highly enriched uranium programme and nuclear proliferation.
"We don't have the answers we need," she said.
At the end of the six-party process, "we have to have the abandonment of all programmes, weapons and materials."
The declaration delivered as part of the deal lists the North's nuclear facilities and the size of its bomb-making plutonium stockpile but does not cover weaponry.
On Friday the North blew up the cooling tower at its Yongbyon reactor to affirm its commitment to disarmament.