In a press conference aboard his jet as he returned from a trip to South Korea, Francis also mentioned the possibility of retiring from the Papacy if he felt he could no longer perform his duties.
His predecessor, Benedict XVI stepped down last year, an almost-unprecedented move that opened the way for Francis’s accession to the Papal throne.
‘I see it as the generosity of the people of God. I try to think of my sins, my mistakes, not to become proud. Because I know it will last only a short time,’ he said.
Then, apparently light-heartedly, he added: ‘Two or three years and then I’ll be off to the Father’s House.’
While the Pope has not spoken publicly before about when he might die, a Vatican source said he had previously told those close to him that he thought he only had a few years left.
Although the Francis is 77, he has been the most vigorous Pope in years, his energy proving the key to his popularity.
His frank admission may lead commentators to speculate as to whether he has any undisclosed health problems.
At the time of his elevation to the Papacy, reports emerged that Francis had a lung removed when he was a teenager in Argentina after suffering an infection.
Dr William Schaffner, chairman of preventive medicine at Vanderbilt University Medical Center in Nashville, Tennessee, said at the time: ‘Obviously, this was a success because here he is at age 76.
‘So whatever they did got him over that precarious period.’
As people age they generally become more susceptible to lung infections, such as pneumonia and bronchitis, according to the National Institutes of Health.
The risk increases if they have pre-existing conditions such as a weakened immune system or heart disease.