Washington (CNN)President Donald Trump's stunning decision to meet with North Korea's despotic leader, Kim Jong Un, might have originated in his administration's campaign to squeeze the country economically and diplomatically, but it was triggered by some deft diplomatic maneuvering by South Korea.
How South Korea triggered Trump's flip from 'fire and fury' to 'call me maybe'
Several current and former officials and diplomatic sources say Secretary of State Rex Tillerson's maximum pressure campaign pushed North Korea into a vulnerable position where it was ready to talk, but it was the recent climate of improved relations between North and South Korea that brought about Trump's remarkable decision.
"It was the last three weeks," one diplomatic source said, referring to the diplomatic blitz prompted by North Korea's participation in the Olympics in Pyeongchang, South Korea, which included a visit from Kim's sister Kim Yo Jong. "South Korea put this all together with a lot of help from North Korea. South Korea knew that despite the noise coming from Washington, from McMaster and company about military action and the bloody nose, that if they dangled this meeting in front of Trump, he could not turn it down. They knew how to play him."
The South Korean government, elected on a campaign promise to engage with Pyongyang, made a calculation that it could undercut US administration officials calling for a more military minded approach to North Korea by appealing to Trump's vanity and love of a star turn, not to mention a dramatic twist in the storyline, and win him over to diplomacy.
Some five months after Trump had tweeted that "I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man," the President has made a complete 180 and is planning to engage in the highest level of diplomacy possible by meeting Kim face to face.
Administration officials say Trump was open to the possibility of dialogue even as he was threatening to rain "fire and fury" down on North Korea, threats that many say helped get Pyongyang to the table. Tillerson himself told reporters that dialogue was something Trump had "had on his mind for quite some time."
But Seoul gave him a nudge.
The bombshell invitation that the South Korean delegation brought to their meetings in Washington was so unexpected that Tillerson was in Africa on a long-planned trip, sending his deputy John Sullivan in his place.
Many observers question the suddenness of the announcement and the lack of conditions attached.
"To me it seemed like an impetuous decision by Trump," said Bruce Klingner, a senior research fellow at the Heritage Foundation and former CIA division chief for Korea.
He points to the fact that the US didn't seem to ask North Korea for anything in return, when it could have pushed for the release of three Americans being held captive there, or a statement from Pyongyang confirming the promises South Korea made on Kim's behalf.
"It's the highest coin in the realm of diplomacy, and Trump seems to have spent it without getting anything in return," Klingner said. "You lost a lot of your negotiating leverage right away."
While Trump's pledge sent shock waves worldwide, the President's unpredictability doesn't guarantee that it's going to happen. On Friday, White House spokeswoman Sarah Sanders tried to walk back expectations and impose conditions.
When the announcement had been made, Sanders had simply said Trump "will accept the invitation to meet with Kim Jong Un at a place and time to be determined" and that the US looks "forward to the denuclearization of North Korea." She added that sanctions and the "maximum pressure" campaign would remain in place, but mentioned no caveats.
Friday, she returned to stipulations the administration had previously issued: that North Korea take concrete steps toward denuclearization. "We're not going to have this meeting take place until we see concrete actions that match the words and the rhetoric of North Korea," Sanders said.
According to South Korea, North Korea has committed to stop nuclear and ballistic missile testing and to denuclearization. It's one of many details that will have to be ironed out in what is, diplomatically speaking, the blink of an eye, as the Trump-Kim summit is proposed for May.
Former officials and Korea experts say that's a highly ambitious time frame to arrange such a high-stakes summit between two countries that have had little contact. Many point to the fact the State Department is depleted with key vacancies in roles related to North Korea as the special envoy for North Korea policy has just resigned and no ambassador to Seoul is in place.
"I think the administration will be constrained, in that its roster is plagued by some critical vacancies and also the bench seems thin on Korean expertise," Klingner said.
Undersecretary of State Steve Goldstein pointed to the acting assistant secretary for East Asia and Pacific affairs, Susan Thornton, along with staff at the embassy in South Korea, saying that "we'll be fully prepared to provide the President" with the support he needs for the summit.
"Now you have a two-month scramble with a counterpart you haven't been interacting with," Klingner said. "It's going to make it very difficult."
Administration officials will likely want a very scripted or controlled environment in the summit, Klingner said, "because you don't want your principle to be surprised. But the playbook may go out the window as soon as the two leaders get in the same room."