The Americans, Kim Dong Chul, Kim Hak-song and Kim Sang Duk, are travelling back to the US with Secretary of State Mike Pompeo, who called on North Korean leader Kim on Wednesday during a previously unannounced visit to Pyongyang.
Trump said North Korea has released the three Americans and he would be there to receive them at the airport in the wee hours of Thursday.
"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 announced in a tweet.
"Secretary Pompeo and his "guests" will be landing at Andrews Air Force Base at 2:00 A.M. in the morning. I will be there to greet them. Very exciting!" Trump said in another tweet.
The fate of the detainees has been a key factor in the build up to the Trump-Kim meeting.
While Kim Dong Chul has been in North Korean custody since before Trump was elected, the other two detainees were arrested last spring, after Trump's inauguration and as tensions between Washington and Pyongyang were beginning to ramp up, CNN reported.
Kim Sang Duk and Kim Hak-song, who were arrested in April and May of 2017, respectively, were both accused of carrying out "hostile acts" against the Kim regime.
Both worked at the Pyongyang University of Science and Technology, which bills itself as the only privately run university in the North Korean capital.
Trump had hinted at a potential development in their case last week in a tweet: "As everybody is aware, the past Administration has long been asking for three detainees to be released from a North Korean Labor camp, but to no avail. Stay tuned!"
The release of the three Americans are seen as a goodwill gesture ahead of a historic summit between Trump and Kim in the coming weeks.
White House spokeswoman Sarah Sanders said that Trump "appreciates" the move and "views this as a positive gesture of goodwill".
Pompeo travelled to North Korea to prepare for the summit between Trump and the North Korean leader Kim.
Trump also said the date and place for the meeting has been set.
"Also, good meeting with Kim Jong Un. Date & Place set," Trump said referring to the meeting Pompeo had with the North Korean leader.
Kim trying to set good conditions for meeting with Trump: Pompeo
North Korean leader Kim Jong un is trying to set good conditions for his meeting with Trump, Pompeo said.
He also said that the place and date for the summit has been locked and would be announced soon.
"I think that Chairman Kim is trying to set good conditions for the summit, right. We are having good conversations, productive conversations. So, I think the work that President Trump has done to put us in this place made this possible," Pompeo told a group of reporters travelling with him.
Last month he travelled to Pyongyang secretly. At the time he was the CIA Director.
Pompeo said that the meeting was very productive and that they have set a date and place for the meeting. He hoped that the name of the venue and date would be announced at the beginning of next week.
"We are planning on it, will be a single day, but in the event that there is more to discuss, there'll be an opportunity for it to extend into the second day as well," Pompeo said in response to a question.
He stayed in Pyongyang for about 13 hours, during which he met Kim.
"We had a chance to talk substantively about what we intend to be on the agenda, and also how we're going to begin to coordinate in the days ahead between now and the summit in a way both sides are confident that we will set the conditions for a successful meeting between the two leaders," he said.
Describing the release of three Americans, who were on his plane, he said this is incredibly exciting.
"They seem to be in good health," he added.
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