The White House has been in control of the early stages, in large part because the relationship between Trump and Secretary of State Rex Tillerson had gone south over policy and personality differences.
Then, Trump abruptly fired Tillerson and announced his intention to nominate Pompeo, the CIA director, as his replacement. White House officials cited the North Korea talks as one rationale for making the change now.
That significantly changes the equation. Pompeo is closer to Trump on personal and ideological levels and already has established a rapport and a degree of trust with him. That means he could play a bigger role in the North Korea talks than Trump ever would have delegated to Tillerson.
Under normal circumstances, summits are extremely choreographed affairs involving lots of preliminary meetings on everything from the shape and size of the table to setting expectations and a road map for getting there.
It usually takes months, though some foreign policy analysts argue the most meaningful tasks can be compressed into a few weeks.
"You have to anticipate three or four ways things could really go bad and figure out how to respond if North Korea directs conversations in one direction," said Michael O'Hanlon, who analyses national security issues for the Brookings Institution.
"If I were working there, we could write a halfway decent memo in the next 48 hours and have it on the president's desk to read over the weekend at Mar-a-Lago. And you have to coordinate with your allies and China. That takes maybe another week or two.
"Two months is a short time. But two months is not too short."
The timing is further complicated by a decision Trump must make on the Iran nuclear deal in mid-May, around the same time he is to meet with Kim. That is when he has threatened to reimpose sanctions on Iran, suspended after the 2015 nuclear agreement was reached. If he does, it could have far-reaching implications on the North Korea talks.
"Right now we have one nuclear crisis," said Tom Countryman, a former State Department official responsible for arms control who was let go at the beginning of the Trump Administration. "We could easily have two about 60 days from now."
He added: "If the President walks out of the Iran deal, he creates a situation that makes it far harder to reach an agreement with North Korea. If I were a North Korean leader, I certainly would not have any confidence in a deal signed with a President who tears up binding commitments so easily."
For the time being, however, there are more questions than answers about how the summit will be structured and what it can reasonably achieve.
The North Korean side has not publicly acknowledged its offer to meet, which was conveyed by a South Korean delegation that visited Pyongyang and then flew to Washington to debrief US officials on the North's willingness to consider abandoning its nuclear weapons.
Some Korean experts said the silence from North Korea is to be expected.
"They are hardly going to behave like a normal counterpart as the US prepares for a summit meeting," said Victor Cha, a Korea expert at Georgetown University who was considered to become Trump's ambassador to Seoul.
"Every second of a summit is scripted and requires a level of detailed planning not just on each side, but between the two sides that will just not be available in the North Korea case."
Nor has the US side offered much detail.
State Department officials said the White House is taking the lead in planning the summit, pointing specifically to the National Security Council's senior director for Asian affairs, Matthew Pottinger. But the White House has not outlined what it expects to achieve and what negotiations might entail.
One reason for the shortage of details is that the summit is occurring out of the regular order. Usually leaders come in at the end of lengthy negotiations that can take months or even years. In this case, they are meeting before any talks have taken place outside clandestine channels. Even the word "summit" may be a bit grandiose for the modest achievements that can be realistically anticipated.
"At a minimum, what you need to achieve is a piece of paper that identifies a set of principles going forward," Miller said. "You're not going to get verification measures. You're not going to get relief on sanctions at the summit."
Even if the summit is restricted to a list of principles, Trump will have to be prepared for some basic issues such as whether the United States will demand the release of three Americans imprisoned in North Korea.
Trump doesn't have a strong background on the Korean Peninsula and is famously uninterested in his daily intelligence briefing, so it is not known how much time he will devote to preparations. No US ambassador has been named to South Korea, either, depriving the Administration of another source of advice.
That would leave ample room for Pompeo, if confirmed, to play a major role in setting the substance and the tone of the talks.
Some of his previous comments could come back to haunt him. Last year, he mused at a public forum about regime change in Pyongyang. Later in the year, the CIA chief made a joke about not asking him about it should Kim suddenly "vanish."
But given that the two leaders have swapped insults, with Trump calling Kim a madman and Kim labeling Trump a "mentally deranged U.S. dotard," perhaps Pompeo's words will be considered mild.
