Sticking point on Trump-Kim talks: Location, location, location

Even as matters of substance like the scope of the summit and the composition of the delegations are being sorted through, the two sides remain at odds over the logistical details, according to US and other officials familiar with the matter.

During CIA Director Mike Pompeo's secret Easter weekend visit to North Korea, Kim personally promised that denuclearization would be a topic of discussion during the meeting with Trump, two sources familiar with the meeting told CNN. Another administration official familiar with the talks described Kim as "personable and well prepared" for the discussion.

But the venue for the talks remains the main sticking point, that official and several others familiar with the matter said.

Pompeo's visit to Pyongyang, according to Trump in a tweet Wednesday morning, "went very smoothly." He added that "denuclearization will be a great thing for the world, but also for North Korea!" and "details of Summit are being worked out now."

At Mar-a-Lago later Wednesday, Trump hailed Pompeo's personal chemistry with the North Korean despot.

"He just left North Korea, had a great meeting with Kim Jong Un and got along with him really well, really great," Trump said. "And he's that kind of a guy. He's really smart but he gets along with people."

Possible locations

US officials have narrowed possible locations for the historic talks to a handful of sites in Asia and Europe, according to two people familiar with the matter. Those officials said that previously discussed sites -- including Washington, Beijing, Seoul and Pyongyang -- have either been ruled out or are now considered less likely.

Trump told reporters on Tuesday that there were five locations under consideration, none of which are in the United States.

In Southeast Asia, Singapore has been viewed as a likely possibility, with cities in Vietnam and Thailand also under consideration. Switzerland and Sweden are also possibilities, along with other European countries who maintain diplomatic relations with North Korea.

The Mongolian capital, Ulaanbaatar, is also seen as a possibility, though is not considered as likely as the other locations.

US officials say the location for the talks is subject to a number of factors, including how far Kim is willing or able to travel by train or airplane.

More pressing, the officials said, is managing the optics of a location that appears neutral to both sides. Kim, for example, is believed to be unwilling to meet on a US aircraft carrier off the Korean coast. Trump, meanwhile, may be unwilling to travel to the demilitarized zone lest he be viewed as arriving on Kim's home turf.

One US official said the North Korean capital, Pyongyang, is not an option for meeting, in the view of officials, who described it as all but impossible to secure and protect from bugs and nerve agents.

As long as a site for the talks remains undecided, officials have been unable to identify a date for the event. Trump and the White House maintain they are aiming for a summit by late May or early June.

Secret talks

Secret talks between North Korean and US intelligence officials have been ongoing for weeks, as CNN has previously reported. South Korean intelligence officials have a long history of working very closely with US counterparts; there is one US official paired to nearly every official working in South Korean intelligence and they often work side by side -- in Seoul and other areas like Afghanistan.

National security adviser John Bolton, in just 10 days on the job, has already met with his counterparts from South Korea and Japan, two sources familiar with the meetings told CNN. He met both national security advisers on the same day last week, and was received fondly.

It was a "very substantive meeting," according to Matt Pottinger, the top Asia official on the National Security Council, who said Bolton's talks included a "very clear exchange of views on planning for both of these summits."

It's possible Bolton and Pompeo will return to Pyongyang before the summit takes place, the sources familiar with the meetings said.

Additionally, a "hotline" between the two Korean leaders is being set up this week, a topic discussed by South Korean Cultural Minister Do Jong-hwan on Tuesday. According to a source familiar with the planning, arranging a hotline is difficult technically and otherwise, and officials are still deciding where to install it -- -- inside the South Korean President's office or a nearby agency.

The cultural minister also told reporters in Seoul that South Korea will be seeking a peace treaty during those discussions that would formally end the Korean War, which technically is still underway even though hostilities ended more than six decades ago.

Trump, currently hosting Japanese Prime Minister Shinzo Abe at Mar-a-Lago, said on Tuesday that South Korea had his "blessing" to seek an end to the Korean War during next week's inter-Korean summit, parts of which could be aired live, according to South Korean President Moon Jae-in.