North Korea has agreed to declare and disable all its nuclear facilities by the end of this year, the US negotiator at talks with Pyongyang in Geneva said.
North Korea has already shut down its main reactor at Yongbyon
Christopher Hill said details of the deal would be discussed at six-party talks in China, later in September.
North Korea tested a nuclear device last year, but has since agreed a deal to shut down its programme in return for economic and other aid.
It has already shut down its main nuclear reactor at Yongbyon.
Mr Hill was speaking after meeting North Korea's top nuclear negotiator, Kim Kye-gwan, for two days in Geneva.
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Under earlier 2005 deal, N Korea agreed to end nuclear programme and return to non-proliferation treaty
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Mr Hill said the talks were "very good and very substantive".
"One thing that we agreed on is that the [North] will provide a full declaration of all of their nuclear programmes and will disable their nuclear programmes by the end of this year, 2007," he said.
Mr Hill had earlier said there could be no normalisation of US-North Korea ties without a nuclear agreement.
But he said: "To the extent that we can move quickly to de-nuclearisation, we can move quickly to normalisation."
Mr Kim said: "We made it clear, we showed clear willingness to declare and dismantle all nuclear facilities."
The six-party negotiations involve the two Koreas, China, Russia, the US and Japan.
The North agreed in principle to halt nuclear work in return for economic and diplomatic benefits two years ago but the process has been slow and fraught with difficulties.
US envoy Christopher Hill said the talks were "very good"
Problems continued even after a more concrete agreement was reached in February this year.
A wrangle over North Korean funds frozen in a bank in Macau held up the closure of Yongbyon. The issue was finally resolved and the reactor shut.
The North then received 50,000 tons of heavy fuel oil from South Korea.
A further 950,000 tons is dependent on ending all nuclear programmes.
Observers suggest Washington now seems prepared to remove North Korea from its list of countries backing terrorism, but it has yet to make its conditions clear.