Nuclear-tinged threats. Name-calling. Missiles flying over Japan. Emergency war council meetings. And now, a face-to-face meeting.

President Donald Trump and North Korean leader Kim Jong Un have sparked fears of a mushroom cloud conflict between two nuclear-armed countries. But in the unpredictable Trump era, their Tuesday morning summit in Singapore seems a fitting next chapter for the two heads of state.

Trump and his senior aides have tried to manage expectations for the first meeting between sitting U.S. and North Korean leaders, saying the two sides are unlikely on Tuesday to sign a final pact to disarm the Asian country. But even Republican lawmakers say the GOP president must extract some concessions from Kim.

That’s because the North already has achieved some goals, even before the two leaders have an expected historic handshake in Singapore. Trump has dropped his “maximum pressure” rhetoric while also assuring Kim he will not be ousted after he has given up his atomic weapons and expressing a willingness to eventually remove sanctions; trade with China has picked up again; and Kim has gained some legitimacy that he can use for his internal messaging.

[(VIDEO) What to Watch as Trump Heads to Historic North Korea Summit]

And on Monday, Secretary of State Mike Pompeo appeared to hand the dictator another victory, saying, “We are prepared to take what will be security assurances that are different, unique than America has been willing to provide previously.”

In short, the U.S. wants Kim to agree to give up his atomic weapons. He wants Washington to give him assurances about his post-deal security, sanctions relief and economic aid, which he needs to develop his country. But lawmakers are worried Trump might not get enough in return during his initial talks with Kim.

“I think we need to see that this meeting has real potential,” said Sen. Roy Blunt, R-Mo., a member of the GOP leadership team. “It may take more than one. But I think something positive has to come out of the first meeting.”

Sen. John Kennedy, R-La., said he doubts “very seriously that we’re going to accomplish much at the first meeting.”

“I don’t think it’s fair to raise people’s expectations unnecessarily,” he said. “Ultimately, though, what we have to get is very simple: Kim Jong Un has to give up all of his nuclear weapons and his ability to make new ones.”

Democratic members, however, have their doubts.

Rep. C.A. Dutch Ruppersberger, D-Md., a former ranking member of the House Intelligence Committee, said Trump “has to realize it’s not about him, it’s about the endgame and results.”

“We can’t have someone like that to have nuclear weapons and threaten people,” he said. “So far, I’ve been concerned about his threats and his rhetoric, and his compulsion to make decisions based on watching a morning TV show. It’s more about endgame. … He has to listen to his experts.”

Illinois Democratic Sen. Tammy Duckworth applauded Trump for having “paused the reckless rhetoric” about “fire and fury” and possible U.S. military action. “Any agreement must instead lead to the dismantling of every aspect of north Korea’s nuclear missile program, including the country’s sizable fissile material stockpile,” she said in a Monday statement, also urging Trump to opt against allowing to Kim to secure commitments about reducing the size of the U.S. military footprint in the region.

[Trump: Kim Gets ‘One-Time Shot,’ Allies on Notice Over Trade]

Former national security officials and analysts say a sweeping pact is unlikely to come together by the time the two leaders depart on Tuesday.

Victor Cha, who was director for Asian affairs at the National Security Council under President George W. Bush, said the “likely reality is that the summit will produce something in between these two extremes.”

“The irony … is that what was initially presented as a cliff-hanger dramatic summit, upon which war or peace on the Korean peninsula hung is now looking more like conventional diplomacy for the unconventional Trump White House,” Cha told a Senate Foreign Relations subcommittee last week.

The administration’s long-term goal is what is described in diplomatic-speak as “complete, verifiable, and irreversible dismantlement” of the North’s nuclear weapons arsenal and its long-range missile fleet. But Pompeo on Monday used a term Kim and his government has frequently used in internal messages: “complete denuclearization” of the Korean Peninsula.

The two sides have yet to publicly state they agree on the definition of denuclearization, which could complicate both Tuesday’s talks and future rounds. But Cha said success for Trump on Tuesday is easier to describe — “a definitive commitment” from Kim to give up his nuclear arms and long-range missiles while also agreeing to a process for future talks.

Security experts say Trump’s goal of convincing the youthful leader to surrender his nuclear arms is a longshot at best.

Paul Haenle of the Carnegie–Tsinghua Center says it is “difficult to see a scenario where Kim agrees to give up his nuclear weapons program – something he and his father and grandfather before him said is critical to the regime’s survival.”