Mike Pompeo expected to return with three American detainees, says South Korean official

US Secretary of State Mike Pompeo is expected to return with three Americans held in North Korea, a South Korean presidential official said on Wednesday. The official said that during Pompeo's visit to North Korea he was expected to finalise the date of an unprecedented summit planned between US President Donald Trump and North Korean leader Kim Jong-un.

Pompeo arrived in Pyongyang on Wednesday to prepare an unprecedented summit between North Korean leader Kim Jong Un and Donald Trump, while the US president signalled the possibility that three Americans detained in the country could soon be released.

Trump earlier broke the news of Pompeo's second visit to North Korea in less than six weeks and said that the two countries had agreed on a date and location for the summit, though he stopped short of providing details.

A US media pool report said Pompeo arrived in Pyongyang, the North Korean capital, from Japan and headed to the city's Koryo Hotel for meetings.

While Trump said it would be a "great thing" if the American detainees were freed, Pompeo, speaking to reporters en route to Pyongyang, said he had not received such a commitment but hoped North Korea would "do the right thing." Pompeo said his visit was intended to finalise a summit agenda that could enable a "historic, big change" in relations between long-time foes.

The detainees' release could signal an effort by Kim to set a more positive tone for the summit, which is being planned for late May or early June, following Kim's recent pledge to suspend missile tests and shut Pyongyang’s nuclear bomb test site.

While Kim would be giving up the last of his American prisoners, 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 in his bid to get Pyongyang to abandon its nuclear arsenal, something it has not signalled a willingness to do.

"Plans are being made, relationships are building," Trump said of the planned summit during remarks otherwise focused on his decision to pull the United States out of the 2015 Iran nuclear deal.

"Hopefully, a deal will happen. And with the help of China, South Korea and Japan, a future of great prosperity and security can be achieved for everyone," Trump said.

Pompeo made a secret visit to North Korea over the Easter weekend, becoming the first US official known to have met Kim, to lay the groundwork for the planned summit. The meeting occurred before Pompeo, who was then head of the CIA, had received Senate confirmation as secretary of state.

Trump suggested that dropping out of the Iran nuclear accord, which he has frequently denounced as a bad deal, would send a "critical message" not just to Tehran but also to Pyongyang."The United States no longer makes empty threats. When I make promises, I keep them," Trump said.

But critics of Trump's decision to leave the Iran deal say it could undermine his credibility in North Korea's eyes, fuelling doubts whether he would abide by any nuclear agreement.