North Korea may have just announced a major concession ahead of talks with President Donald Trump.

According to South Korean President Moon Jae-in on Thursday, North Korea is ready for “complete denuclearization,” meaning that it would stop improving its nuclear weapons and missiles that can hit America and its allies. What’s more, North Korea would do that — and the US can keep its troops in South Korea.

If North Korea is seriously considering that, it would be a marked shift from its past stance. When Pyongyang usually talks about denuclearization, US troop removal is always a sticking point. Pyongyang fears that US troops are only waiting to invade North Korea, and so it wants to keep its nuclear arsenal to deter that incursion. But now, it’s possible America’s 28,500 troops on the Korean Peninsula can stay as North Korea winds down its program.

Pyongyang’s new stance, if true, could change the tenor of Trump’s potential meeting with North Korean leader Kim Jong Un in late May or early June. Abraham Denmark, a former top Asia security official at the Pentagon, tweeted on Thursday that North Korea’s announcement could mean Trump and Kim may strike an agreement.

“Looks like a deal may actually be coming together,” Denmark said. “Shaping up to be a comprehensive package that involves a peace regime, denuclearization, and eventual normalization of relations.”

On Wednesday, Trump expressed his wishes for a good meeting with Kim — but promised not to engage if it goes awry before or during the face-to-face. “If I think that it’s a meeting that is not going to be fruitful, we’re not going to go,” Trump said at Mar-a-Lago alongside Shinzo Abe, the Japanese prime minister. “If the meeting, when I’m there, is not fruitful, I will respectfully leave the meeting.”

North Korea’s announcement, via Moon, comes just two days after CIA Director Mike Pompeo’s secret meeting with Kim over Easter weekend became public. And the policy change will surely affect Kim and Moon’s April 27 summit to discuss a formal peace treaty — which would formally end the Korean War. (Right now both sides have signed an armistice, not a peace treaty, which means the countries are technically still at war.)

Don’t get too excited about the end of North Korea’s nuclear program yet. We’ve been here before.

It would be a great thing if the US could trust North Korea’s new position. But diplomacy with North Korea is hard for one simple reason: Pyongyang promises a lot but then doesn’t follow through.

For example, as the New York Times noted, North Korea has consistently told the US and South Korea that it can live with American troops on the peninsula since the 1990s. “It is desirable that US troops stay as a peacekeeping force in Korea, instead of a hostile force against the North,” Kim Jong Il, the former leader of North Korea and Kim Jong Un’s father, reportedly said at a 2000 meeting between the two Koreas.

But then North Korean leaders usually go back to the same talking point: North Korea can’t give up its nuclear program because of the threat posed by the US military and its allies South Korea and Japan.

On top of that, the US and other countries have been trying to come to a diplomatic, negotiated agreement with North Korea over its nuclear program since 1985.

They got really close twice. In 1994, the US and North Korea signed the Agreed Framework, in which the North agreed to freeze its plutonium weapons program in exchange for two proliferation-resistant nuclear power reactors and fuel oil from the United States.

But the agreement collapsed in 2002, and by January 2003, the North had resumed its nuclear program.

Then in August 2003, the international community launched the so-called “Six Party Talks,” designed to get North Korea to halt its nuclear program through negotiations with five countries: China, the United States, South Korea, Japan, and Russia.

Two years later, in September 2005, it looked like the talks might work — North Korea formally agreed to abandon “all nuclear weapons and existing nuclear programs” in exchange for energy assistance from the other countries. Joseph DeTrani, who led those negotiations from the American side, told me today’s diplomatic outreach was “a positive development” and that it reminds him of the 2005 agreement.

Yet in 2009, amid disagreements over technical details related to verification, North Korea walked out on the talks. It said it would never return to the negotiations and maintains that it is no longer bound by their agreements. Pyongyang has been ramping up its nuclear and ballistic missile programs ever since.

So when I asked Harry Kazianis, an Asia security expert at the Center for the National Interest think tank, if the US should take North Korea’s reported new stance seriously, he demurred.

“Nope, we should not,” he told me. “I am hopeful, but not stupid.”