CIA Director Mike Pompeo, President Donald Trump’s pick to be the next secretary of state, met with North Korean leader Kim Jong Un over Easter weekend.

That’s a big deal: Pompeo is the first senior US official to meet a member of the ruling Kim family since October 2000 — and the first ever to meet with Kim Jong Un himself. The face-to-face comes just a month or so before Trump is set to sit down with Kim for a historic summit, and it’s likely Pompeo and Kim used part of their time together to hash out the details of that forthcoming meeting.

Trump confirmed Pompeo’s trip to Pyongyang in a tweet on Wednesday morning, saying the “Meeting went very smoothly and a good relationship was formed. Details of Summit are being worked out now.” Just the day before, he told reporters that the US and North Korea had spoken at “extremely high levels” without mentioning Pompeo’s name.

The Pompeo-Kim meeting has sparked optimism that the Trump-Kim summit might actually happen. “Many criticized the president for going into a head-of-state summit without holding working-level talks first,” says Matthew Kroenig, a nuclear expert at Georgetown University, “so this should be received as good news that Pompeo is laying the groundwork necessary for a productive meeting.”

But danger remains, especially if Kim uses the summit to extract major concessions from Trump. “This should raise our probabilities that Trump will go into the summit intending to emerge with a ‘deal’ — almost certainly not a good one — and definitely not one that results in denuclearization but something he can hail as a win,” says Mira Rapp-Hooper, an Asia security expert at Yale Law School.

“Kim has every incentive to play that game too,” she adds.

Trump and Kim may strike a deal. It just might not be what Trump wants.

North Korea launches a missile in September 2017.

Chung Sung-Jun/Getty Images

Trump and Kim may not be on the same page when they discuss denuclearization, and that’s a problem.

That’s because the US and North Korea define it differently. Washington has a straightforward view: North Korea ends its nuclear and missile programs and allows international inspectors to ensure Pyongyang doesn’t reconstitute them.

North Korea has a more grandiose outlook: It wants the US to stop threatening to destroy it, end its nuclear protection of South Korea and Japan, and likely remove the 28,500 US troops from the Korean Peninsula.

The two leaders will likely hash this out if they meet. Kim has repeatedly said he’s willing to discuss denuclearization with Trump, and Trump has hyped the possibility of denuclearization in his Wednesday morning tweet, writing that “Denuclearization will be a great thing for World, but also for North Korea!”

But it’s not clear Trump gets the nuance of what Pyongyang means by denuclearization.

“There are CIA analysts who know that but the information may not trickle up,” says Van Jackson, a North Korea expert at the Victoria University of Wellington. But, he warns, Trump may suddenly come to understand how different the two sides’ views are while “in the room with a charismatic personality getting the dirt straight from their mouth.”

There’s an even bigger worry: Kim could dangle “denuclearization” in front of Trump in hopes of receiving something North Korea has wanted for decades — that is, the removal of all US troops from the Korean Peninsula and the end of America’s protection of South Korea and Japan.

There are issues with that when you dig into the specifics. Retired Marine Lt. Gen. Chip Gregson, the Pentagon’s top Asia official from 2009 to 2011, explains that Kim might “offer to eliminate his ability to strike the US” — that is, get rid of his intercontinental ballistic missiles — “while retaining a massive threat to South Korea and Japan.” That might sound great to Trump, but it would be a disastrous outcome for South Korea and Japan — and a massive breach of trust between the US and those two close allies.

If Trump agrees to that, which he might, “it would mean the end of our alliances and go a long way to persuade our allies that they should pursue their own nuclear capability,” says Gregson.

Trump has repeatedly complained that the US is “losing money” by protecting South Korea with US troops without getting any substantial financial compensation in return. During a rally in Missouri on March 14, Trump lamented the US relationship with South Korea, telling the crowd: “We lose money on trade, and we lose money on the military. We have right now 32,000 soldiers on the border between North and South Korea. Let’s see what happens.” That’s music to Kim’s ears, since Pyongyang has wanted US troops removed from the Korean Peninsula for decades.

That bombs-for-troops deal would be much, much less than what Trump probably has in mind right now, but it would allow him to say he guaranteed America’s safety while reducing the military’s global footprint.

That kind of agreement, though, may actually be the extent of what Trump can get from Kim. Most experts say there’s little to no chance Kim would agree to give up his nuclear or ballistic missile programs. Pyongyang worked hard to attain the ability to hit the US with a nuclear weapon, which it wants in part to safeguard against possible invasion by American and South Korean forces.

But Adam Mount, a nuclear expert at the Federation of American Scientists, says it’s better that Trump and Kim agree to something. “Even a thin and largely symbolic agreement is far preferable to war,” he told me when I spoke to him last month. “What we should avoid is giving away issues of strategic or diplomatic importance for an agreement that doesn’t make us safer.”