Early in his presidency, Donald Trump began his approach to the enduring North Korean nuclear-weapons crisis with an unproductive, unpresidential war of words with North Korean leader Kim Jong Un that threatened to go beyond Twitter. So the move from his “Little Rocket Man” and “fire and fury” phase to today’s diplomatic process is progress indeed.

Trump tweeted that “there is no longer a Nuclear threat from North Korea” after his historic meeting with Kim in Singapore last year. But a more recent, more reasoned U.S. intelligence agency analysis stated that North Korea, while not conducting any nuclear-capable missile or nuclear weapons tests in a year, is still “unlikely to give up all of its [weapons of mass destruction] stockpiles, delivery systems, and production capabilities.”

That made the Singapore summit a symbolic success for Kim, who despite having a heinous human-rights record and a reckless nuclear weapons and ballistic missile program, got to stand on stage as an equal to a U.S. president. Conversely, it was a substantive failure for Trump and, more profoundly, for a world justifiably jittery over Kim’s arsenal.

After striking out on a substantive agreement in Singapore, Trump must make more verifiable progress when he meets Kim on Wednesday and Thursday in Hanoi.

While it’s unlikely there will be a commitment from Kim for full denuclearization, that should remain the ultimate objective. Secretary of State Mike Pompeo accurately confirmed that the North is still a nuclear threat and said that there is no plan to remove sanctions. But Trump’s post-Singapore rhetoric has already reduced the resolve of other world leaders to maintain strict sanctions, and Trump’s qualified support of key regional alliances has no doubt factored into Tokyo’s and Seoul’s calculus, too.

There are other inducements to move Kim toward more specific, verifiable goals, however, including the prospect that the president may leverage a declaration of a formal end to the Korean War, which Pyongyang has long pushed for. While there is understandable concern among some military and diplomatic experts that this could result in Kim calling for a reduction, or elimination, of the 28,500 U.S. troops keeping the peace on the Korean Peninsula, the nonbinding measure, short of a formal peace treaty, would recognize reality: The U.S. and North Korea are not at war, and in fact are encouragingly engaging in a diplomatic process to try to ensure regional peace. And it’s consequential that Seoul’s views be considered, and South Korean President Moon Jae-in has pushed for such a declaration.

Another idea that might be valuable is the establishment of liaison offices in Pyongyang and Washington. But none of these measures substitute for specifics on a “serious diplomatic plan” called for by eight senior Senate Democrats. In a letter to the president, they wrote that “we believe your next meeting with Kim thus must demonstrate tangible, verifiable, progress and denuclearization and reducing tensions with the North.”

Many foreign policy experts concur, including those from the Carnegie Endowment for International Peace, who called for six “realistic benchmarks to make clear progress,” including a “road map and timeline” on immediate and intermediate steps toward a “comprehensive, verifiable cap on North Korea’s nuclear arsenal, including its delivery capabilities.”

Toby Dalton, co-director of Carnegie’s Nuclear Policy Program, told an editorial writer that priority one is “a North Korean commitment to a freeze that is more than just vague words from Kim Jong Un, but defining what he means when he says that they are no longer producing nuclear weapons.”

Vague words are summit standards, so what’s needed are verifiable deeds. But it is encouraging that words — and not hostile ones — are being exchanged, and the world should wish for the summit’s success.