President Trump says he will “talk denuclearization” at his planned summit with North Korean leader Kim Jong Un — a word he has emphasized to underscore the tough line he plans to take in the most surprising foreign policy development of his presidency.

But the diplomatic buzzword can mean different things to different players on the world stage. The success of Trump’s gambit probably hangs on whether he and Kim can agree on what it means for them and whether it’s worthwhile to keep fudging the details of a term that U.S. and Asian diplomats have been fudging for years.

The unwieldy term is typically part of a stock phrase, “denuclearization of the Korean Peninsula,” that U.S. officials have used for more than a decade to mean that North Korea would abandon its nuclear weapons.

Those weapons are the main leverage that North Korea holds, whether it sits down to bargain or not, and Kim has publicly declared that he will never give them up.

For him, denuclearization probably means, at most, some far-off possibility that he will downsize or get rid of his country’s nuclear arsenal, which he can dangle as leverage for help averting economic catastrophe and shoring up his family dynasty, Asia experts said. To Kim, it may also mean assurances that the United States won’t replace the nuclear weapons it pulled out of South Korea more than 25 years ago. It could even mean the end of the large deployment of U.S. forces there.

“When they say it, it means it’s a long-term objective. And when they hear Americans say it, they think Americans want to just do it right away, and that’s not acceptable to them,” said Joel S. Wit, a former U.S. adviser and negotiator who worked on the Clinton-era Agreed Framework nuclear pact with North Korea.

“As a long-term objective, I believe it will be acceptable” to Kim, especially if left a bit undefined at the start, said Wit, a senior fellow at the U.S.-Korea Institute at the Johns Hopkins School of Advanced International Studies.

“They’re not going to be Gaddafi,” he said, referring to Libyan dictator Moammar Gaddafi and his 2003 decision to renounce a less-developed nuclear program and seek stable relations with the United States. He was overthrown eight years later.

It’s hard to know what enigmatic Kim means by the phrase or what he expects for the meeting. Official North Korean media has not mentioned a word about the summit nearly a week after it was announced in dramatic fashion on the White House driveway by South Korean officials.

In 2016, official state media said North Korea supports the “denuclearization of the whole Korean Peninsula, and this includes the dismantlement of nukes in South Korea and its vicinity.”

The phrase has been left deliberately vague for years.

As a tool to encourage negotiation, it can sound less off-putting to North Korea as well as to other major players such as China than, say, “eradication of all North Korean nuclear weapons and the means to make them.”

The thinking goes that squishy language helps get negotiations started by giving everyone a little cover.

At the same time, Trump and the three previous presidents have insisted that “denuclearization” be the basis for negotiations because the phrase stakes out a maximal goal. To U.S. political hawks skeptical that any engagement with North Korea can pay off, it means that the United States is saying upfront that it won’t settle for a mere reduction or rollback of advanced weapons and ballistic missile programs.

Seen in that context, the term can be an “excuse” for U.S. leaders to refuse to talk at all, said Jessica Lee, policy director at the Council of Korean Americans.

“Trump may insist on complete, verifiable and irreversible denuclearization of North Korea, in keeping with past presidents’ policies,” Lee said. “Kim Jong Un will think of denuclearization as a process, a movement toward a certain direction. But Kim won’t ‘denuclearize’ past the point of giving up what he thinks is necessary to defend his country unless there are security guarantees from the United States.”

That means assurances that the United States won’t try to overthrow the Kim family or invade the country, as well as guarantees about the U.S.-South Korean military alliance. North Korea calls Washington its primary enemy.

South Korea has begun its own talks with North Korea, part of a warming trend that was on global display at the Winter Olympics last month, and is playing intermediary between Kim and Trump.

North Korean leaders have sought a summit with U.S. presidents before, but White Houses of both parties have said such a meeting would reward the Kim regime by granting parity with the president of the United States. Seasoned negotiators also see such a meeting as the capstone to a step-by-step process that would flesh out things like what “denuclearization” really means.

Trump stunned South Korean government envoys who came to Washington last week to encourage U.S. participation by accepting Kim’s invitation on the spot. Trump quickly insisted that he hadn’t given away the store.

“Kim Jong Un talked about denuclearization with the South Korean Representatives, not just a freeze. Also, no missile testing by North Korea during this period of time. Great progress being made but sanctions will remain until an agreement is reached. Meeting being planned!” Trump tweeted Thursday.