Donald Trump has cast doubt over whether his highly-anticipated meeting with Kim Jong-un, the North Korean leader, will go ahead next month.
"It may not work out for June 12," Mr Trump said. "If it does not happen, maybe it will happen later."
Mr Trump was holding talks with South Korean President Moon Jae-in at the White House.
The US president added that he does believe the North Korean leader is willing to give up nucler weapons, amid fears about apparent North Korean backpedaling.
"I do think he is serious. I think he is absolutely very serious," Mr Trump said.
"He will be extremely happy" Trump said of Kim, if the deal works out. "He will be very happy."
Mr Trump went on: "You never know about deals...I’ve made a lot of deals. You never really know."
He added: "You'll know soon."
The president declined again to say whether he had yet spoken personally to Kim.
He added that North Koreans were "hardworking, great people".