Washington (CNN) The Trump administration is scouting locations for a second summit between President Donald Trump and North Korean leader Kim Jong Un, despite the fact that talks between North Korea and the United States appear to be at a stalemate, according to two sources familiar with the planning process.

On Wednesday, Trump struck an upbeat tone as he waved what he called a "great letter" from Kim in front of reporters and his Cabinet in the Oval Office. Trump did not reveal what it said but sources familiar with the letter said it was designed to remind Trump of the strength of their relationship and maintain the President's enthusiasm for the process.

The last time Trump received a letter from Kim was in September, after Trump canceled Secretary of State Mike Pompeo's visit to North Korea, citing a lack of "sufficient progress" on denuclearization.

That letter changed Trump's tone.

"He wrote me beautiful letters," Trump said at a rally shortly afterward. "And they're great letters. We fell in love."

The following month Pompeo traveled to North Korea and met with Kim. Yet there was no new progress on tangible denuclearization from the visit.

One of the sources familiar with the contents of the latest letter tells CNN that Kim seems to send letters to Trump when he feels like things have gone quiet or when he wants to remind Trump about the strong rapport they struck up in Singapore. Another source who has been told about the letter from Kim said this one was also "predictably effusive."

The view of some in the administration is that Kim is sending the letters to keep Trump enthusiastic about their relationship, appeal to Trump's ego and provide a buffer for when Pompeo and others tell him that North Korea is failing to follow through on its Singapore commitments, so he can point to the letters and say he's developed this great relationship.

Best thing 'since sliced bread'

"I would think it says I want to see you soon, you are the best thing that has happened since sliced bread. Then I think it was going on to say we are willing to work with you on denuclearization," explains Joe Yun, the former US State Department special representative for North Korea and a CNN contributor. Yun has not seen the letter itself but is very familiar with the way Kim operates.

The administration sent scouting teams to multiple locations in different regions, including Asia, during the last few weeks of 2018. US officials have not formally shared these locations with the North Koreans, and the list could potentially expand.

The scouting began before Trump told reporters that the White House would be setting up a meeting with Kim in the "not too distant future." Experts say it could take a few months for the summit to come to fruition, given the early stages the administration is in on planning.

The last Trump-Kim summit took place in Singapore last June, and as of now that country is not on the list for the next meeting. Each of the locations officials have traveled to have "pros and cons," according to a source familiar with the process. When asked about the summit's planning the National Security Council referred questions to the State Department, and due to the partial government shutdown the department has not yet responded.

But at this point, one foreign diplomat told CNN it seems the administration has not yet involved South Korea in planning efforts, though US officials had stressed the importance of coordinating logistics with key allies ahead of Trump's first meeting with Kim.

South Korean officials have often stated their support for a second meeting between Trump and Kim, and while indications suggest Seoul has not yet been consulted in the administration's hunt for a location, the same diplomatic source told CNN the preference would be for it to take place in an Asian country. The North Koreans, meanwhile, have said they would like the summit in Pyongyang.

Vietnam, Indonesia, Hawaii, Mongolia and the demilitarized zone between North and South Korea have all been floated by foreign diplomats and North Korea experts as potential locations for the next summit.

Switzerland proposal fell apart

Logistical issues have already caused at least one summit proposal to fall apart, according to an administration official, who told CNN that the White House reached out to North Korea in an attempt to get Kim to Switzerland for a meeting with Trump but the two sides were unable to make it happen due to travel concerns.

The administration had initially thought Switzerland would be a good place for Kim because he had gone to school there in the late 1990s. But part of the problem was that Kim remained sensitive about criticism he had received for using a Chinese plane to travel to Singapore for the first summit, the official said.

The White House declined to comment on the suggestion that the administration had attempted to persuade Kim to go to Switzerland.

As the White House continues location scouting, Steve Biegun, US special representative for North Korea, has been repeatedly shut out of any direct talks with his counterparts. Biegun had hoped to meet with his North Korean counterpart last fall in Vienna, Austria. When it became clear after more than a week that the North Koreans were not going to meet him there, he was told to come home. There was then an expected meeting in New York that also fell apart.

Despite frustrations, Biegun is not giving up. The former Ford Motor executive is, however, a "little more realistic" about the challenges that come with the job, according to a source familiar with the communication between the two countries. Biegun did travel to Pyongyang with Pompeo in October but that is the last time he has met with North Koreans face-to-face. He did meet with South Korean officials in October.

Meanwhile, the administration is also dealing with the retirement of CIA Korea Mission Center chief Andrew Kim, whose familiarity with North Korean officials cast him as one of the most integral players in greasing the wheel for diplomacy with Pyongyang.

Andrew Kim, who is of Korean descent, had taken the lead on providing intelligence assessments examining all the issues that could affect Kim Jong Un's thinking and approach to the negotiations, including the impact of US-backed economic development and efforts to maintain the loyalty of his top military commanders.

He was thrust into the spotlight last year after traveling to North Korea alongside Pompeo multiple times and he served as the translator in meetings with Kim Jong Un.

Details about Andrew Kim's replacement, who remains unnamed, are scarce but sources told CNN the individual has spent a number of years on the North Korean issue and has been a key part of previous high-stakes negotiations.

However, CNN has also learned that this person does not speak Korean, which is a challenge given that Andrew Kim often served as a high-level negotiator and a translator in the meetings.

"I can't imagine that many people are as well qualified as Andy Kim. He established the Korea Mission Center. From everything I have heard it is a very well functioning center," says David Maxwell, a senior fellow at the Foundation for Defense of Democracies who previously served in the US Army in Japan and South Korea.

Two US officials insisted that the intelligence community is always prepared to fill the gap until new talent is brought in. Those officials also made clear that the intelligence community would prefer to keep details related to Andrew Kim's replacement under wraps at this time, noting it is unusual for officials in this type of role to receive the kind of publicity that was seen with Kim.