A senior State Department official briefed reporters separately as Pompeo and Kim Yong Chol met late on Wednesday.
Kim would be wise to delay any official visit to Russian Federation until after his meeting with Trump, said Jeong Hyung-gon, a research fellow at the Korea Institute for International Economic Policy. USA officials have repeated the four elements so frequently that they refer to it casually by the initials CVID.
"Between now and if we're going to have a summit, they're going to have to make clear what they're willing to do", said the official.
"We've seen tremendous amounts of progress" toward the summit, State Department spokeswoman Heather Nauert said. "But as far as I can tell, that is not based on any evidence beyond Kim Jong Un's statements, which I don't think are very plausible". "And we're planning as if it is happening", she said.
That contradicts the United States policy of maximum pressure.
"We're moving forward, and we'll be prepared either way".More news: Weinstein was released on bail
The adviser, Dr Siegfried Hecker, a former director of the Los Alamos weapons laboratory in New Mexico and now a Stanford professor, argues that the best the United States can hope for is a phased denuclearisation that goes after the most risky parts of the North's programme first. Instead, their pitch is that Pyongyang will gain more security by abandoning its nuclear program, allowing it to escape from the yoke of worldwide sanctions and isolation and concentrate on economic prosperity.
Pompeo tweeted after the dinner: "Good working dinner with Kim Yong Chol in NY tonight".
He said his personal denuclearisation estimate ran to 15 years, given the tangle of political and technical uncertainties that the U.S. and North Korea would face if they went ahead and sought a historic accord.
"Sergei Lavrov, foreign minister of the Russian Federation, arrived here on Thursday at the invitation of Ri Yong Ho, foreign minister of the Democratic People's Republic of Korea (North Korea)", KCNA news agency said in a brief dispatch. Kim is the highest-ranking North Korean official to visit the U.S.in 18 years.
US Secretary of State Mike Pompeo gets into a vehicle after meeting with Kim Yong-chol on Wednesday.
His visit comes amid a flurry of diplomatic activity to organise next month's summit, with US Secretary of State Mike Pompeo also meeting Kim's right-hand man Kim Yong Chol in NY late Wednesday.More news: UAE Consulate in Kerala issues advisory over Nipah outbreak
The White House said on Wednesday that negotiations at the demilitarized zone along the border between North and South Korea for the summit were going well and that it expects the historic meeting to take place on June 12.
Halting or suspending many of these will likely take less than a year, the authors estimate, but eliminating or setting limits on them will take six to 10 years.
The delegation in Singapore is discussing the logistics of a gathering, to be held June 12 or afterward.
The Associated Press reports Pompeo met with Kim Yong Chul, the country's former military intelligence chief and a top aide in Kim's government.
Senior officials are meeting in NY in the U.S., while mid-level officials are meeting in Panmunjom, the truce village in the Demilitarized Zone between the two Koreas, and working-level officials are meeting in Singapore, the venue for the big event.
Mr. Pompeo began his discussions with Gen. Kim by hosting a dinner on Wednesday night.More news: Not hosting: Auburn will hit road for NCAA Regional
He was accused by South Korea of masterminding deadly attacks on a South Korean navy ship and an island in 2010.