Pope Benedict XVI will publish the first of two volumes of a book he is writing on the life of Jesus Christ in the spring, the Vatican said Tuesday.

Benedict will publish the 10 chapters he has written so far because he doesn't know "how much time and strength" he has left, the Vatican said in a statement.

Benedict, shown giving a prayer in September, wrote the book to refute modern interpretations of Jesus as nothing more than a revolutionary and moral teacher.
(Plinio Lepri/AP)

Since his election as the Pope, he has made several public references to being old and not knowing how much more time God will give him.

The Pope says the book should not be considered part of official, binding Roman Catholic teaching.

It is "my interpretation of the figure of Jesus of the New Testament," he said.

The first book, called Jesus of Nazareth, will cover Jesus's life from his baptism in the River Jordan to the Transfiguration, the point at which three of his apostles had visions of Moses and Elijah and saw the divine nature of Christ.

The biography seeks to refute modern interpretations of Jesus as nothing more than a revolutionary and moral teacher. These interpretations are confusing to the faithful, Benedict said.

Italian publisher Rizzoli, a unit of RCS Mediagroup, will publish the book in co-operation with the Vatican's publishing house.

Benedict wrote dozens of books in his previous role as Cardinal Joseph Ratzinger, but this is his first since becoming Pope. His encyclical, God is Love, was published in February.

The German-born theologian says he started writing the book during his summer holidays in 2003 when he was still a cardinal because he wanted to reflect on the "long personal journey" of his faith.

"After my election to the episcopal seat, I used up all my free time to continue working on it," he said in a statement to the Ansa news agency.

The book is "solely a reflection of my personal research," he said and should not be considered infallible.

"Therefore, everyone is free to contradict me," he said.

Benedict's predecessor, Pope John Paul II, was also a prolific writer and his Crossing the Threshold of Hope was an international best-seller.

With files from the Associated Press