Donald Trump’s meeting with North Korean leader Kim Jong Un is scheduled to last about four hours. Add in translation time and a few pleasantries, and there’s likely to be at most two-and-a-half hours of substantive discussion (though that could change if the leaders want to keep talking). It’s not clear if anything can be accomplished in such a short time—or whether foreign policy establishments in Washington, Tokyo and Beijing even want progress to be made.

The summit, which begins in Singapore Tuesday morning, marks the first time a U.S. president will sit down to negotiate with the leader of a country with which, technically, the U.S. is still at war. This meeting is also unusual because traditionally, when heads of state meet, the details not only of what will be discussed, but what will be agreed upon, are negotiated in advance. There’s no pre-cooked deal this time. There’s barely agreement about the ingredients.

After an initial, promising meeting between then-CIA director Mike Pompeo with Kim in Pyongyang in April, the North retreated into non-communication and then into harsh rhetoric after new national security adviser John Bolton suggested that the “Libya model” should apply to North Korea. Bolton claims he meant only that Pyongyang had to give up its entire nuclear arsenal and allow detailed international inspections to verify that the deed is done. But Pyongyang apparently took “Libya” to be a threat: Several years after Tripoli stood down its weapons program, dictator Muammar Gaddafi was killed in an anti-regime uprising backed by NATO air power.

After Trump bailed on the meeting, South Korean President Moon Jae-in intervened, meeting with Kim Jong Un for a second time in just weeks. Kim then had a trusted aide hand deliver a letter from him to Trump, and the meeting was back on. Now, for the third time in the last 25 years, the U.S. will try to get rid of North Korea’s small nuclear arsenal—but this time, the leaders will meet face to face.

Of all the parties with interests in the outcome, only the South Koreans, who dearly want a peace deal with the North to work, seem confident. A diplomatic source in Seoul over the weekend reiterated that the Moon government believes the details Kim will present about “denuclearization” will be sufficient to get the U.S. and the North on a path that will lead to just that: a verifiable stand down of Pyongyang’s nukes, coupled with a U.S. agreement not to have the South be a port of call any longer for air and seaborne nuclear bombs. (The U.S. does not permanently base nuclear weapons in South Korea, but they are rotated in and out on submarines and bombers.)

But the U.S., Japanese and Chinese diplomatic establishments look on Tuesday’s meeting with something between skepticism and dread. In Washington, current and former officials who have dealt with North Korea over the years worry that Trump, in his eagerness for a historic deal, is about to get rolled. Trump has already given Kim three things that Pyongyang wants: de facto recognition as a nuclear power (why else would Trump be there if not for the nukes?); the prestige of a one-on-one summit with a U.S. president, with the entire world’s media in attendance; and the relaxing of economic sanctions. China has already backed off some of the economic strictures it was imposing, and Trump himself has said that pending the meeting, the U.S. is no longer applying “maximum pressure” to Pyongyang.

Foreign policy analysts say Trump could be tempted to accept a vaguely worded pledge from the North about denuclearization and then agree to a peace treaty with Pyongyang, officially ending the Korean War. He has already publicly raised the notion of reaching a peace agreement with North Korea, and U.S. aides say the subject will definitely come up at the summit. Why is that a potential problem? Because it could trigger a huge shift in the U.S.-created security architecture of east Asia.

Pyongyang would not even have to ask for the removal of 28,000 troops from South Korea, points out Michael Green, who ran east Asia policy for George W. Bush’s National Security Council: Kim could just wait a short while and then say, “We have a peace treaty, why do you need your troops here? Why do you need missile defense, we have a peace treaty? Why do you need military exercises, we have a peace treaty?”

The potential for change in the U.S.’s force posture on the Korean peninsula unsettles neighboring Japan, whose government has felt like a bystander in this entire process. That’s why Prime Minister Shinzo Abe wanted a recent White House meeting with Trump, and has asked North Korea for his own meeting with Kim. Tokyo worries that Trump’s isolationist instincts will lead him to reduce the U.S. presence not only in Korea but eventually in Japan as well. A senior White House foreign policy adviser, not authorized to speak for the record, says that’s just not going to happen. But Tokyo worries nonetheless, given how quixotic Trump’s foreign policy appears to be.

Beijing has the opposite concern. The fact that President Xi Jinping called Kim Jong Un back to China for a second, pre-summit meeting a month ago suggested that the Chinese were nervous about Kim’s intentions. A nuclear deal and a peace treaty could lead the U.S. and South Korea to move toward a full-on embrace of the North, trying to pull it into their orbit, and out of Beijing’s. China currently has the only meaningful economic and diplomatic relationship with Pyongyang, and it’s not clear that Chinese leaders want that to change.

Bolton, who will be at Trump’s side as national security adviser, has a history of being extremely skeptical of North Korean promises. He effectively ended the first nuclear agreement with the North, negotiated in 1994 by the Clinton administration. Bolton is a stickler for details, and will insist that the two sides add lots of them—and quickly—to any broad agreement that might be struck in Singapore. That would likely include intrusive verification measures that the North might not abide, even if they are not the full “Libya model” Bolton had talked about. In other words, while Trump, Kim and Moon are looking for a deal, the diplomats who don’t want dramatic change may be the ones who get their wish.