U.S. President Donald Trump welcomed three former U.S. prisoners at a military base near Washington on Thursday, thanking North Korean leader Kim Jong Un for their release and sounding upbeat on a planned summit between the two sides. The prisoners, freed after U.S. Secretary of State Mike Pompeo traveled to the North Korean capital, landed at Joint Base Andrews outside Washington, where a giant U.S. flag was suspended between ladders of two fire trucks on the edge of the taxiway. "Frankly we didn't think it was going to happen and it did," Trump said after thanking Kim for releasing the men. "We’re starting off on a new footing. This is a wonderful thing that he released the folks early." Trump said he believed Kim wanted to bring North Korea "into the real world" and was hopeful of a major breakthrough at their planned meeting. "I think we have a very good chance of doing something very meaningful," Trump said. "My proudest achievement will be - this is part of it - when we denuclearize that entire peninsula." Trump and Kim engaged in a bellicose exchange of rhetoric last year over North Korea's development of nuclear missiles capable of reaching the United States in defiance of U.N. Security Council resolutions. Tensions began to ease, coinciding with the North's participation in the Winter Olympics in South Korea in February. Details of the planned summit have yet to be announced, but one U.S. official said Singapore had emerged as the most likely venue. Trump said it would be held in a few weeks' time. A White House spokeswoman said the three former prisoners would be taken to Walter Reed National Military Medical Center in nearby Maryland for further medical evaluation.
The three Americans formerly held hostage in North Korea gesture next to US President Donald Trump, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
The three Americans formerly held hostage in North Korea gesture next to US President Donald Trump and Secretary of State Mike Pompeo, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
US President Donald Trump greets the Americans formerly held hostage in North Korea upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Joshua Roberts
US President Donald Trump shakes hands with one of the three Americans formerly held hostage in North Korea, next to first lady Melania Trump, US Vice President Mike Pence and his wife Karen, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Joshua Roberts
President Donald Trump talks to the media next to the Americans formerly held hostage in North Korea, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Joshua Roberts
One of the Americans formerly held hostage in North Korea gestures next to US President Donald Trump and first lady Melania Trump, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
US President Donald Trump and first lady Melania Trump greet the Americans formerly held hostage in North Korea, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
One of the Americans formerly held hostage in North Korea gestures next to US President Donald Trump and first lady Melania Trump, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
President Donald Trump talks to the media next to the three Americans formerly held hostage in North Korea, Tony Kim, Kim Hak-song and Kim Dong-chul, upon their arrival at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Joshua Roberts
The three Americans formerly held hostage in North Korea, Tony Kim, Kim Hak-song and Kim Dong-chul, walk next to US President Donald Trump, first lady Melania Trump, US Vice President Mike Pence and US Secretary of State Mike Pompeo at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
President Donald Trump waves as he arrives with first lady Melania Trump to greet the three Americans formerly held hostage in North Korea, at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
The US flag is seen on the tarmac before the arrival of the three Americans released from detention in North Korea, at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jonathan Ernst
US Vice President Mike Pence and second lady Karen Pence arrive to greet the three Americans formerly held hostage in North Korea, at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
White House Chief of Staff John Kelly looks on before to greet the arrival of the three Americans formerly held hostage in North Korea, at Joint Base Andrews, Maryland, US, May 10, 2018. REUTERS/Jim Bourg
FILE PHOTO - A combination photo shows a Korean Central News Agency (KCNA) handout of Kim Jong Un released on May 10, 2016, and Donald Trump posing for a photo in New York City, US, May 17, 2016. REUTERS/KCNA handout via Reuters/File Photo & REUTERS/Lucas Jackson/File Photo
North Korean leader Kim Jong Un shakes hands with US Secretary of State Mike Pompeo in this undated photo released on May 9, 2018 by North Korea's Korean Central News Agency (KCNA) in Pyongyang. KCNA/via REUTERS
North Korean leader Kim Jong Un meets with US Secretary of State Mike Pompeo in this May 9, 2018 photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang May 10, 2018. KCNA / via REUTERS
US Secretary of State Mike Pompeo greets an unidentified North Korean general on arrival at the Pyongyang, North Korea, May 9, 2018. Matthew Lee/Pool via REUTERS
Secretary of State Mike Pompeo bids farewell to senior North Korean official Kim Yong Chol, director of the United Front Department, which is responsible for North-South Korea affairs, and Foreign Minister Ri Su Yong on his departure from Pyongyang, North Korea, May 9, 2018. Matthew Lee/Pool via REUTERS
A man who identified himself as Kim Dong Chul, who previously said he was a naturalized American citizen and was arrested in North Korea in October, attends a news conference in Pyongyang, North Korea, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang, North Korea on March 25, 2016. KCNA via Reuters/Files