The United States says it is ready to resume talks with North Korea after Pyongyang pledged to dismantle its key missile facilities and suggested it may close its main Yongbyon nuclear complex.
US Secretary of State Mike Pompeo has invited North Korea's foreign minister to meet in New York next week, with the aim of completing its denuclearisation by January 2021, after a Pyongyang summit between the leaders of the two Koreas.
The US appeared eager to seize on commitments by North Korean leader Kim Jong-un at his talks with South Korean President Moon Jae-in even as critics said the steps did little to put Pyongyang on a course for irreversible denuclearisation.
North Korea will allow experts from "concerned countries" to watch the closure of its missile engine testing site and launch pad at Dongchang-ri, Moon said at a joint news conference with Kim.
North Korea will also take additional steps such as closing its main Yongbyon nuclear complex if the US undertook unspecified reciprocal measures, Moon added.
The sudden revival of diplomacy followed weeks of doubts in US President Donald Trump's administration's about whether North Korea was willing to negotiate in good faith after a June summit between Trump and Kim yielded few tangible results.
The January 2021 completion date was the most specific deadline set in what is expected to be a long process of trying to get the North to end its nuclear program, which may threaten US allies South Korea and Japan as well as the US homeland.
Pompeo said Washington has also invited Pyongyang's representatives to meet the US special representative for North Korea, Stephen Biegun, in Vienna at the "earliest opportunity."
Speaking before Pompeo's announcement, two senior US officials involved in US-North Korea policy voiced fears that Kim was trying to drive a wedge between Washington and Seoul.
US officials suggested Kim is trying to ease economic pressure on him to curb his nuclear programs and to undercut the rationale for US troops being based in South Korea by improving relations between Pyongyang and Seoul.
"There is nothing the North has offered so far that would constitute irreversible movement toward denuclearisation, however you define that, by January 2021 or any other time, or even a reduction of the military threat it poses to the South and the region," said a US intelligence official.
"Everything that's out there now is conditional on US actions that would reduce the pressure on the North to cooperate or (is) filled with loopholes and exit ramps," added the official, who spoke on condition of anonymity.
Even if North Korea were to shut down Yongbyon, officials and experts believe it has other secret nuclear facilities.
Satellite images and other evidence in recent months have suggested North Korea is continuing to work on its nuclear program clandestinely.
Despite the doubts of US officials and outside analysts, North Korea's pledge at the summit with the South Korean president drew an enthusiastic response from Trump.