North Korea released three American prisoners and handed them over to US Secretary of State Mike Pompeo on Wednesday, clearing a major obstacle to an unprecedented summit between President Donald Trump and North Korean leader Kim Jong Un.

The men, who were freed after Pompeo met Kim, were on the way home from Pyongyang on the chief US diplomat's plane. The president planned to greet them when they land at Andrews Air Force Base outside Washington at around 2 a.m. EDT (0600 GMT) Thursday morning.

The release, which was praised by the White House as a "gesture of goodwill," appeared to signal an effort by Kim to set a more favourable tone for the summit and followed his recent pledge to suspend missile tests and shut a North Korean nuclear bomb test site.

While Kim is giving up the last of his American detainees, whom North Korea has often used as bargaining chips with the United States, a release could also be aimed at pressuring Trump to make concessions of his own as he tries to get Pyongyang to abandon its nuclear arsenal, something it has not signalled a willingness to do.

The release gave Trump a chance to tout a diplomatic achievement just a day after his decision to pull out of the Iran nuclear deal drew heavy criticism from European allies and others.

"I am pleased to inform you that Secretary of State Mike Pompeo is in the air and on his way back from North Korea with the 3 wonderful gentlemen that everyone is looking so forward to meeting. They seem to be in good health," Trump wrote on Twitter.

“I appreciate Kim Jong Un doing this and allowing them to go," Trump told reporters at the White House. He also thanked Chinese President Xi Jinping, saying Beijing was "helpful" in securing the men's freedom.

The family of Tony Kim, one of freed prisoners, said in a statement: "We are very grateful for the release of our husband and father, Tony Kim, and the other two American detainees."

The fate of the three Korean-Americans had been among a number of delicate issues in the run-up to the first-ever meeting of US and NorthKorean leaders, which is being planned for early May or late June.

As Pompeo returned to his Pyongyang hotel from a 90-minute meeting with Kim, the secretary of state crossed his fingers when asked by reporters if there was good news about the prisoners.

A North Korean official came to the hotel shortly afterwards to inform Pompeo that Kim had granted them "amnesty," according to a senior US official present for the exchange.

Pompeo replied: "That's great," according to the official.

"You should make care that they do not make the same mistakes again," the North Korean official was quoted as saying. "This was a hard decision."They were in the air less than an hour after leaving custody.

Asked what his first words were to the freed Americans, Pompeo told reporters on his plane: "I welcomed them back. They were happy to be with us on this plane, to be sure."

The three are Korean-American missionary Kim Dong-chul; Kim Sang-duk, also known as Tony Kim, who spent a month teaching at the foreign-funded Pyongyang University of Science and Technology (PUST) before he was arrested in 2017; and Kim Hak-song, who also taught at PUST.

North Korean state media says they were detained either for subversion or committing "hostile acts" against the government. Many of the foreigners detained by North Korea in the past have said the government forced them into making confessions to false or trumped-up charges.

'Very Productive'

Speaking to reporters as he returned from North Korea, Pompeo said his meetings with the North Koreans were "very productive." The two sides agreed to "meet again in person to finalise the details," a US official said.

Trump said agreement had been reached on a date and venue for the summit and details would be announced within three days.

The meeting will not take place at the heavily fortified demilitarised zone between North and South Korea, he said. Trump has also previously cited Singapore as another possible site.

"There is reason for some optimism that these talks could be fruitful," US Defense Secretary Jim Mattis said of the coming summit after the detainees' release. He said, however, that the US troop presence in South Korea would not be part of initial negotiations with North Korea.

There was also no sign that Pompeo's visit had cleared up the question of whether North Korea would be willing to bargain away nuclear missiles that might threaten the United States.

Trump has credited his "maximum pressure" campaign for drawing North Korea to the negotiating table and has vowed to keep sanctions in place until Pyongyang takes concrete steps toward denuclearisation.

But former spy chief Kim Yong Chul, director of North Korea’s United Front Department, said in a toast to Pompeo over lunch in Pyongyang: “We have perfected our nuclear capability. It is our policy to concentrate all efforts into economic progress in country. This is not the result of sanctions that have been imposed from outside.”

U.S. officials had been pressing Kim to free the three remaining American detainees as a show of sincerity before the summit. Trump and Kim have exchanged insults and threats over the past year but tensions have eased in recent months.

Until now, the only American released by North Korea during Trump's presidency has been Otto Warmbier, 22, a university student who returned to the United States in a coma last summer after 17 months of captivity. He died days later.

Warmbier's death escalated US-North Korea tensions, already running high at the time over Pyongyang's stepped-up missile tests.

North Korea reminded the United States on Wednesday there still was tension between them, warning it against "making words and acts that may destroy the hard-won atmosphere of dialogue," the North's state media said.

First Published:May 10, 2018 6:05 AM IST