US President Donald Trump has said there is a "very substantial chance" a historic summit with North Korea's Kim Jong-un next month may not happen.
He said the North must meet conditions for the summit to go ahead though if it did not, it might happen "later".
He was speaking as he received South Korea's President Moon Jae-in at the White House.
The North has said it may cancel the summit if the US insists on it giving up nuclear weapons unilaterally.
Mr Trump did not say what conditions the US had set for the summit but, asked by a reporter about the North's arsenal, he said "denuclearisation must take place".
The 12 June summit is due to take place in Singapore. It follows a summit between the two Korean leaders in April.
North Korea is expected to dismantle a nuclear test site this week as a good will gesture but the demolition may be delayed by bad weather.
North Korea cancelled high-level talks with South Korea, saying the South's joint military exercises with the US were a "provocation" and rehearsal for invasion.
Pyongyang then accused US national security adviser John Bolton of making "reckless statements" after he suggested the North could follow a "Libya model" of denuclearisation.
That was a reference to Libya's former leader, Muammar Gaddafi, who agreed to give up nuclear weapons in 2003 and was later killed by Western-backed rebels.
Mr Trump, however, later denied the US would follow the "Libyan model" if an agreement was reached"The model, if you look at that model with Gaddafi, that was a total decimation," he said.
"We went in there to beat him. Now, that model would take place if we don't make a deal, most likely. But if we make a deal, I think Kim Jong-un is going to be very, very happy."
(BBC)
