WASHINGTON — Freed after more than a year in prison, three Americans flew homeward from North Korea late Tuesday toward a big middle-of-the-night celebration featuring President Donald Trump — the latest sign of improving relations between longtime adversaries in the buildup to a historic summit between Trump and North Korea’s King Jong Un.

Trump promised “quite a scene” at Joint Base Andrews outside Washington for the detainees, who were released as Secretary of State Mike Pompeo visited North Korea on Wednesday to finalize plans for the summit.

Singapore was the likely site, late this month or in early June, for Trump’s most ambitious foreign police effort yet.

Trump made a point of publicly thanking North Korea’s leader for the prisoners’ release — “I appreciate Kim Jong Un doing this” — and hailed it as a sign of cooling tensions and growing opportunity on the Korean peninsula.

North Korea had accused Kim Dong Chul, Kim Hak Song and Tony Kim, all Korean-Americans, of anti-state activities. Their arrests were widely seen as politically motivated and had compounded the dire state of relations over the isolated nation’s nuclear weapons.

Trump entered office as an emboldened North Korea developed new generations of nuclear weapons and ballistic missiles capable of hitting the continental U.S. Those advances were the subject of President Barack Obama’s starkest warning shortly before Trump took office, and this is a crisis he’s convinced his negotiating skills can resolve.

Crediting himself for recent progress, Trump has pointed to Kim’s willingness to come to the negotiating table as validating U.S. moves to tighten sanctions — branded “maximum pressure” by the president.  The wee-hours ceremony Thursday was to be an early celebration for an issue that has already put the prospect of a Nobel Peace Prize on Trump’s mind.

“Everyone thinks so, but I would never say it,” he said Wednesday when asked if the award was deserved.

The release capped a dramatic day of diplomacy in Pyongyang. After Pompeo’s 90-minute meeting with Kim Jong Un, he gave reporters a fingers-crossed sign when asked about the prisoners as he returned to his hotel. It was only after a North Korean emissary arrived a bit later to inform him that the release was confirmed.

The three had been held for periods ranging from one and two years. They were the latest in a series of Americans who have been detained by North Korea in recent years for seemingly small offenses and typically freed when senior U.S. officials or statesmen personally visited to bail them out.

The last American to be released before this, college student Otto Warmbier, died in June 2017, days after he was repatriated to the U.S. with severe brain damage.

Warmbier was arrested by North Korean authorities in January 2016, accused of stealing a propaganda poster and sentenced to 15 years in prison with hard labor. His parents, Fred and Cindy Warmbier, have filed a wrongful death lawsuit, accusing the government of torturing and killing their son.

“We are happy for the hostages and their families,” the Warmbiers said in a statement Wednesday. “We miss Otto.”