North Korea should take "actual action" towards giving up its nuclear weapons to break the deadlock in talks with Washington, a top security adviser to the South's president said, suggesting Seoul's patience with Pyongyang may be wearing thin.
President Moon Jae-in was instrumental in brokering the negotiations between Pyongyang and Washington, seizing on the 2018 Winter Olympics in South Korea to catalyse a rapid diplomatic rapprochement after a year of missile tests, threats and tensions.
But the first summit between the North's leader Kim Jong Un and US President Donald Trump in Singapore in June produced only a vague commitment to "work toward complete denuclearisation of the Korean peninsula".
Their second meeting in Hanoi last month broke up without agreement, or even a joint statement, as the two failed to come to a deal over sanctions relief and denuclearisation.
Since then, Pyongyang has said it is considering suspending the talks and images have emerged of rebuilding works at the Sohae rocket launch facilities.
That triggered international alarm that North Korea might be preparing a long-range missile or space launch, which could put the whole negotiations process at risk -- Pyongyang has not carried one out for more than a year and Trump has repeatedly said its continued moratorium is crucial.
A launch of any kind by the North would be a "disaster", said Moon's special adviser on national security Moon Chung-in.
The "outcome will be catastrophic", he told AFP.
In Hanoi, US officials said, Trump urged Kim to "go all in" and that "the weapons themselves need to be on the table". In return, they were "prepared to go all in as well".
But it was not clear exactly which facilities at the Yongbyon nuclear complex the North was willing to give up, while they wanted "basically all the sanctions except for armaments" lifted, the officials said.
For its part the North's foreign minister said it only wanted some of the measures eased, and that its proposal to close "all the nuclear production facilities" at Yongbyon was its best and final offer.
Moon's goal, his adviser said, was a "nuclear weapons-free, peaceful and prosperous Korean peninsula" -- and he would not accept a peaceful accommodation with a nuclear-armed North.
The South Korean president has long pushed engagement with Pyongyang to bring it to the negotiating table, but his security adviser backed US Secretary of State Mike Pompeo's assessment that "talk is cheap", saying that the North had given "words and commitment, but no actions".