Prince Harry quipped that Barack Obama would see his serious face if he paused for too long as he interviewed him for the BBC.
The former US president was being interviewed by Prince Harry as part of his guest editorship of Radio 4’s Today Programme which will be broadcast on December 27.
Kensington Palace said the interview was recorded during the Invictus Games in Toronto in September.
Today tweeted a video clip showing Harry and Mr Obama warming up ahead of the chat, with the former president joking: "Do I need a British accent?"
Harry told his interviewee that if he used long pauses between answers he would probably get "the face".
Mr Obama said: “Do I have to speak faster because I’m a slow speaker?”
Harry replied: “No, no, not at all.”
Smiling cheekily, Mr Obama then said: “Do I need a British accent?”
Harry quipped back: “If you start using long pauses between the answers, you’ll probably going to get the face.”
Laughing, Mr Obama said: “Let me see the face.”
When Harry showed him what he meant and adopted a stern expression, Mr Obama said: "I don't want to see that face."
Harry later said: “You’re excited about this and I’m nervous about it, that’s what’s quite funny.”
Mr Obama replied: “It’s fun. I’ll interview you if you want.”
The prince responded laughing: “No, no, let’s keep it this way I’d much prefer that.”
The palace said the conversation features Mr Obama talking about his plans to focus on cultivating the next generation of leadership through the Obama Foundation.
Harry, who was recently at the inaugural summit of the Obama Foundation in Chicago, has forged a strong bond with the Obamas, through his work with servicemen and his trips to America.
At this year's Invictus Games, Mr Obama reportedly quizzed Harry on his romance with Meghan Markle as they watched the wheelchair basketball.
Mr Obama was among those to congratulate Harry and Meghan on their engagement, writing on Twitter: "Michelle and I are delighted to congratulate Prince Harry and Meghan Markle on their engagement.
"We wish you a lifetime of joy and happiness together."