Pope Francis says in a new book that he can relate to people in intensive care units who fear dying from coronavirus because of his own experience when part of his lung was removed 63 years ago.

Italian newspapers published excerpts of the new book "Let Us Dream: The Path to A Better Future," on Monday ahead of publication next month.

In the book, a conversation with one of his biographers, Briton Austen Ivereigh, Pope Francis talks in some of the most personal terms to date about the time he was hovering between life and death.

"I know from experience the feeling of those who are sick with coronavirus, struggling to breathe as they are attached to a ventilator," he said.

Francis was a 21-year-old seminarian in the second year of his studies for the priesthood in his native Buenos Aires when an illness that had been mis-diagnosed as influenza worsened and he was hospitalised.

"They took about a litre and a half of water out of one lung and I was hanging between life and death," he said.

Several months later doctors removed the upper lobe of his right lung. Today, the 83-year-old Pope can be heard breathing heavily after climbing stairs.

"(The experience) changed my bearings," he said. "For months I didn't know who I was, if I would live or die, even the doctors didn't know. I remember hugging my mother one day and asking her if I was about to die."

Pope Francis recounts how a nun who worked as nurse helped save his life by secretly doubling the doses of penicillin and streptomycin that a doctor had prescribed.

"Thanks to her regular contact with sick people, she knew what patients needed better than the doctor and had the courage to put that experience to work," he said.