US President Donald Trump said he will meet North Korea's Kim Jong Un as originally scheduled on June 12 for a historic summit after extraordinary Oval Office talks with a top envoy from Pyongyang.
Speaking after more than an hour of talks with Kim Yong Chol in the Oval Office, Mr Trump told reporters that denuclearisation - and a formal end to the decades-old Korean war - would be on the table in Singapore.
But the US leader warned that he did not expect to immediately sign a deal to bring a halt to the North's nuclear program.
"I never said it goes in one meeting. I think it's going to be a process, but the relationships are building and that's very positive," he said on Friday, after waving farewell to the North Korean envoy, Mr Kim's right-hand man.
President Trump said they had discussed formally ending the Korean War, which has been largely frozen since an armistice ended hostilities, but not the underlying conflict, in 1953. Since then, there have been occasional clashes on the divided peninsula.
"We talked about it. We talked about ending the war," Mr Trump said.
"Historically it's very important, but we'll see. We did discuss that, the ending of the Korean War. Can you believe we're talking about the ending of the Korean War?"
Washington is determined that Mr Kim should agree to what US officials call the "complete, verifiable and irreversible" end of North Korea's nuclear weapons and intercontinental missile programmes.
Mr Kim says he is committed to "denuclearization" in some form, but he is expected to demand security guarantees - one of which could be an formal end to the conflict with the US and South Korea.
Most expert observers are skeptical that even an unprecedented summit between the two leaders can lead to a rapid breakthrough, and Mr Trump admitted it would be a long and difficult process.
"We're not going to go in and sign something on June 12. We never were. I told him today, 'Take your time'," he said, adding nevertheless that he expects "a really positive result in the end."
Kim Yong Chol, the most senior North Korean to visit the United States in 18 years, spent almost 90 minutes in the Oval Office.
Afterwards, President Trump and US Secretary of State Mike Pompeo walked the North's small delegation to their waiting cars, smiling and shaking hands in front of the media before the motorcade pulled away.
North Korean officials said Kim Yong Chol was expected to return to Pyongyang shortly. Meanwhile, discussions between US and North Korean officials continue in Singapore and in the Demilitarised Zone between North and South Korea.
On Thursday, Kim Jong Un told Russia's Foreign Minister Sergei Lavrov that his commitment to denuclearisation remains "unchanged and consistent and fixed," but experts warn he will seek concessions from Washington.
In addition to an end to the war, he is likely to seek international recognition as well as guarantees against any strike by the US forces stationed in South Korea.
As expected, Kim Yong Chol handed Mr Trump a letter from Kim that may clear up some of the questions. The US leader said the missive was "very nice" - but then admitted he had not yet read it. An aide later confirmed he did after the talks.
The Oval Office talks and letter delivery came only a week after President Trump threatened to consign the entire process to history, abruptly cancelling the summit in a sharply worded letter, only to revive preparations shortly afterwards.
Mr Trump said that, after Friday's talks, the parties are "totally over that and now we're going to deal and we're going to really start a process."
Since the short-lived boycott threat, diplomats from both countries have conducted an intense flurry of talks, culminating this week when Mr Pompeo sat down in New York with Kim's envoy.
North and South Korea agreed to hold more meetings throughout this month to carry out the agreements reached between their leaders at the April summit, according to a joint statement issued after Friday's talks.
Seoul welcomed Mr Trump's meeting with Kim Yong Chol at the White House.
"The delivery of a letter from Chairman Kim Jong Un to President Trump has apparently broadened and consolidated the road to the North Korea-US summit," said Kim Eui-gyeom, spokesman for South Korea's presidential Blue House.
"We will calmly, and with expectation, watch the historic meeting in Singapore."