Benedict, aged 93, has become very frail and his voice is barely audible, author Peter Seewald told the daily.

But at a meeting with Seewald on Saturday, German-born Benedict appeared optimistic, and said he might pick up writing again if he regains his strength, the report said, adding he was suffering from shingles.

Benedict came to his native Bavaria in June to pay his ailing brother Georg Ratzinger a final visit. Ratzinger, aged 96, died shortly afterwards.

It was Benedict's first trip outside Italy since 2013, the year he resigned the papacy.