It also underscores Mr. Trump’s unorthodox approach to one of the riskiest diplomatic gambits of his presidency. However trusted by the president, Mr. Pompeo is hardly a traditional emissary. He is not yet the nation’s chief diplomat but a lame duck as the nation’s spymaster.
Few details about Mr. Pompeo’s trip, which officials said happened over Easter weekend, had emerged on Wednesday morning. But some former administration officials expressed surprise that he returned from Pyongyang without any visible concessions, like the release of three Americans detained in North Korea.
In 2014, the then-director of national intelligence, James R. Clapper, traveled secretly to North Korea to negotiate the release of two Americans, Kenneth Bae and Matthew Todd Miller. Three Korean-Americans — Kim Dong Chul, Kim Sang-duk, and Kim Hak-song — currently are being held on charges of espionage and committing hostile acts toward the North Korean state.
The administration also has not agreed on a date for the meeting of Mr. Trump and Mr. Kim, which officials said pointed to problems in settling on a site for the encounter. On Tuesday, Mr. Trump told reporters the White House was looking at five potential locations.
Some of the potential sites — like Singapore, Sweden, or Switzerland — are far from North Korea, posing a challenge to Mr. Kim’s rickety fleet of aircraft. Others, like the Peace House in the Demilitarized Zone between North and South Korea, could pose an optics problem for the White House, which does not want Mr. Trump to be viewed as traveling to Mr. Kim’s doorstep.
The Mongolian capital, Ulan Bator, has surfaced as a possible compromise. Without a site, however, the White House has been unable to announce a date, though officials are sticking to Mr. Trump’s recent declaration that the meeting will be in late May or early June.
On Tuesday, Mr. Trump added to the mystery surrounding the visit by appearing to confirm that he had been in direct contact with Mr. Kim himself. He later clarified that while the talks were at “the highest levels,” he would “leave it a little bit short of that.”
Mr. Pompeo’s involvement with North Korea predated Mr. Trump’s decision to meet Mr. Kim, several officials said. He has been dealing with North Korean representatives through a channel that runs between the C.I.A. and its North Korean counterpart, the Reconnaissance General Bureau.
He also has been in close touch with the director of South Korea’s National Intelligence Service, Suh Hoon, who American officials said brokered Mr. Kim’s invitation to Mr. Trump.
While a meeting of Mr. Trump and Mr. Kim would be one of the boldest diplomatic gambles of recent years, it was orchestrated largely by the intelligence services of the three countries.
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Officials said Mr. Suh, the South Korean spy chief, laid the groundwork for Mr. Kim’s invitation in negotiations and a subsequent meeting in Pyongyang with Kim Yong-chol, a powerful general who heads inter-Korean relations and used to run North Korea’s intelligence service.
Kim Yong-chol led the North’s delegation to the closing ceremony of the Winter Olympic Games in Pyeongchang, South Korea, where he sat steps from Mr. Trump’s daughter Ivanka. The two did not speak.
Mr. Suh was one of two South Korean envoys who visited the White House to brief Mr. Trump on their meeting with Kim Jong-un in Pyongyang — which led to the president’s impromptu decision to accept Mr. Kim’s invitation.
For Mr. Pompeo, who now has an office at the State Department, the choice to use the intelligence channel was mostly a convenience — allowing him to be involved in the planning while he awaited his move to the State Department.
Still, some officials expressed concern about the C.I.A.’s taking the lead in orchestrating a leader-to-leader meeting — work that would normally be the province of the State Department. It is not clear that Mr. Pompeo took anyone from the State Department with him to North Korea.
The intelligence officials on the North Korean side, they said, are shadowy figures, not least Kim Yong-chol himself, who is accused of masterminding the torpedo attack that sank a South Korean Navy ship in 2010, killing 46 sailors, and a deadly artillery attack on a South Korean island.
The State Department’s role in North Korea dwindled after Mr. Trump publicly split with Mr. Tillerson over his efforts to open a diplomatic channel to the North, initially to obtain the release of the three Americans but also to set the stage for a broader negotiation.
In October, while Mr. Tillerson was in Beijing, Mr. Trump tweeted, “I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man…”
The State Department recently lost its chief North Korea negotiator, Joseph Yun, who retired from the Foreign Service, in part because of his frustration with his agency’s diminished role.
The timing of Mr. Tillerson’s departure, officials said, was not coincidental. Mr. Trump wanted to have Mr. Pompeo in place to handle an opening to North Korea. But Mr. Pompeo has expressed extremely hawkish views about North Korea, suggesting last summer that the United States should push for regime change.
“It would be a great thing to denuclearize the peninsula, to get those weapons off of that, but the thing that is most dangerous about it is the character who holds the control over them today,” Mr. Pompeo said at the Aspen Security Forum.
“So from the administration’s perspective, the most important thing we can do is separate those two. Right?” he said. “Separate capacity and someone who might well have intent and break those two apart.”
Last week, Mr. Pompeo insisted to the Senate Foreign Relations Committee that he had never advocated for regime change.
“Just to be clear, my role as a diplomat is to make sure that we never get to a place where we have to confront the difficult situation in Korea that this country has been headed for now for a couple of decades,” he added.