Donald Trump has claimed parents pleaded with him to bring back the remains of their sons who died in the Korean War 65 years ago.

The US president made the remarks a day after signing a joint statement with North Korean leader Kim Jong-un, in which both countries agreed to “immediate repatriation” of identified soldiers.

“The soldiers that died in Korea, their remains are going to be coming back home,” he told Fox News aboard Air Force One.

“And we have thousands of people that have asked for that, thousands and thousands of people. So many people asked when I was on the campaign, I’d say ‘Wait a minute, I don’t have any relationship…’, but they said, ‘When you can President, we’d love our son to be brought back home’. You know the remains.

“And I asked [Mr Kim], we had pretty much finished, and I said, ‘Will you do me a favour? The remains of these great fallen heroes, can we do something?’ He agreed to it immediately. It was pretty great.”

The comments shocked viewers, who pointed out any parents still alive to make the request of Mr Trump during the 2016 presidential campaign would have been at least in their late 90s, and more likely well over a hundred. The Korean War armistice was signed in 1953.

Donald Trump salutes North Korean soldier at Singapore summit

“My father was a Korean War veteran who would be 90 today,” Maureen McFadden, a TV reporter, wrote on Twitter. “His parents were long gone during the election, as was he.”

Angus Johnston, a US historian, said: “An 18-year-old parent of an 18-year-old soldier killed on the last day of the Korean War would have been 99 years old in 2016. Trump says ‘so many’ of them reached out to him personally during the campaign.”

It was not the only controversial claim made by Mr Trump in the interview with Fox News anchor Bret Baier. He hailed Chinese premier Xi Jinping an “incredible guy”, adding it was “pretty good” he was “essentially president for life”.

He praised Mr Kim as a “tough guy” and a leader with rare ability in response to a questions about the dictator killing North Korean citizens.

The 72-year-old also said he wanted Russia back in the G7 so he could dine with Vladimir Putin and ask him if “you could get out of Syria”.

“I could ask him to do things that are good for the world,” he added.

On Tuesday, Mr Trump hailed his historic meeting with Mr Kim in Singapore a success, despite scepticism from experts.

Singapore Summit: historic first meeting between Trump and Kim Jong-un Show all 20 1 /20 Singapore Summit: historic first meeting between Trump and Kim Jong-un Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim leave following their historic meeting AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim sign a document committing to peace between their nations, amongst other things EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump holds up a document that both he and Mr Kim have signed AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un The two leaders reach out to shake hands for the first time AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim shake hands as they meet for the first time Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim walk off stage, following their historic meeting Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim take a stroll after their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim interrupt their stroll to talk to the media AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim and Mr Trump look out over a balcony at the Capella hotel, where they held their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump takes questions at the press conference following his meeting with with Mr Kim AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump appreciates the crowd in the press conference following his meeting with Mr Kim Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump travels to the Istana ahead of the summit with Kim Jong Un on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Kim Jong Un travels to the Istana ahead of the summit with President Trump on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim poses for a photo with Singapore's Finance Minister Vivian Balkrishnan and Education Minister Ong Ye Kung ahead of the summit with Mr Trump Twitter/Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump shakes hands with Singapore Prime Minister Lee Hsien Loong, meeting on Monday June 11 in the Istana, Singapore's presidential palace AP Singapore Summit: historic first meeting between Trump and Kim Jong-un At a working lunch on Monday, Singapore's Prime Minister surprised Mr Trump with a birthday cake, in early celebration of his 72nd birthday later in the week EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un US Secretary of State Mike Pompeo answers questions about the summit at a press briefing in Singapore on Monday, June 11 Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un US President Donald Trump arrives at the Paya Lebar Air Base in Singapore on June 10, two days prior to his summit with North Korean leader Kim Jong Un Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim met on Tuesday June 12 in the Capella hotel on the island resort of Sentosa, just off the south coast of Singapore AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump boards Air Force One following the summit AFP/Getty

The president said he would stop “expensive, provocative” war games with the South, in return for a North Korean commitment to “work toward complete denuclearization of the Korean Peninsula” – a phrase observers argue is open to different interpretations.

The US “committed to provide security guarantees” to North Korea, according to an agreement signed by both leaders in Singapore following decades of hostilities between the two nations.

Mr Trump said he expected the denuclearisation process to start “very, very quickly”. US secretary of state Mike Pompeo and North Korean officials will hold follow-up negotiations “at the earliest possible date”, the joint statement said.