Pope Francis revealed he has written a resignation letter in case medical problems prevent him from carrying out his duties. 

Francis, speaking to the Spanish newspaper ABC, said he wrote the letter shortly after being elected pontiff in 2013 and handed it to Cardinal Tarcisio Bertone, who then was the Vatican secretary of state. Cardinal Pietro Parolin is now in that role and Francis believes he is in possession of the instruction. 

"I signed it and said: ‘If I should become impaired for medical reasons or whatever, here is my resignation. Here you have it,'" Francis said. 

Francis, who turned 86 on Saturday, had surgery in 2021 to repair a bowel narrowing and has been dealing with knee pain that for months saw him use a wheelchair. Lately, he has increasingly used a cane instead of the wheelchair to get around in public. 

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Pope Francis general audience Vatican

Pope Francis pauses in front of a Nativity scene set up in Paul VI Hall at The Vatican at the end of his weekly general audience, on Dec. 14, 2022. (Massimo Valicchia/NurPhoto via Getty Images)

Francis said he was sure Bertone would have passed on the letter to the current secretary of state. 

He joked that now he has revealed the existence of his resignation note, "someone will run up to [Parolin] (saying), ‘Give me that piece of paper.’" 

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Pope Francis stands with a cane

Pope Francis during the public audience of Confindustria in the Paul VI Hall at Vatican City on Sept. 12, 2022. (Grzegorz Galazka/Archivio Grzegorz Galazka/Mondadori Portfolio via Getty Images)

In past remarks, Francis has hailed the decision of his predecessor, Pope Benedict XVI, to resign because he felt due to advancing age he wouldn't be best able to carry out his duties. 

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Benedict, who is living in a monastery on the Vatican's grounds, was the first pontiff to resign in 600 years, and his stepping down paved the way for Francis' election as the first pope from South America. 

Pope Francis arrives in Kazakhstan in wheelchair

Pope Francis arrives at Nur-Sultan International Airport in Kazakhstan on Sept. 13, 2022. (Filippo Monteforte/AFP via Getty Images)

Francis in the interview played down his mobility challenge, saying, "One governs with the head, not the knee." 

The Associated Press contributed to this report.