VATICAN CITY, Feb 11: Pope Benedict XVI announced Monday he will resign as leader of the world´s 1.1 billion Catholics on February 28 because his age prevented him from carrying out his duties -- an unprecedented move in the modern history of the Catholic Church.
"I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry," the 85-year-old pope said in a speech pronounced in Latin at a meeting of cardinals in the Vatican.
"In order to govern the ship of Saint Peter and proclaim the Gospel, both strength of mind and body are necessary, strength which in the last few months, has deteriorated in me to the extent that I have had to recognise my incapacity to adequately fulfil the ministry entrusted to me," he said.
"For this reason, and well aware of the seriousness of this act, with full freedom I declare that I renounce the ministry of Bishop of Rome, Successor of Saint Peter, entrusted to me by the Cardinals on 19 April 2005, in such a way, that as from 28 February 2013, at 20:00 hours, the See of Rome, the See of Saint Peter, will be vacant and a Conclave to elect the new Supreme Pontiff will have to be convoked by those whose competence it is," he said.
Pope Benedict, who has looked increasingly weary in recent months and often has to use a mobile platform to move around St Peter´s basilica during Church services, had hinted in a book of interviews in 2010 that he might resign if he felt he was no longer able to carry out his duties.
"The pope caught us a bit by surprise," Vatican spokesman Federico Lombardi said at a hastily-arranged press conference.
The only other pope to resign because he felt unable to fulfil his duties was Celestine V in 1296, a hermit who stepped down after just a few months in office saying he yearned for a simpler life and was not physically capable for the office.
Tributes poured in from around the world, with a spokesman for Chancellor Angela Merkel saying the German-born pope deserved "respect" and "gratitude" for his nearly eight years as pontiff.
French President Francois Hollande said the pope´s decision was "eminently respectable".
Benedict, formerly Joseph Ratzinger, succeeded the long-reigning and popular John Paul II in April 2005 after serving nearly a quarter-century as the Church´s doctrinal enforcer, earning himself the nickname "God´s Rottweiller".
His papacy has been marked by his efforts to revive the Catholic faith amid rising secularism in the West, as well as the scandals of child abuse by Catholic priests that was hushed-up for decades.
Benedict has championed Christianity´s European roots and showed his conservatism by repeatedly stressing family values and fiercely opposing abortion, euthanasia and gay marriage.
This recent file picture taken on February 6, 2013 at the Paul VI hall at the Vatican shows Pope Benedict XVI arriving for the weekly general audience. (AFP)
How the pope is chosen
On the death or abdication of a pope, his successor is elected by a college of cardinals meeting in conclave in the Sistine Chapel in the Vatican.
The system of election has been changed several times over the 2,000 years of the papacy´s existence.
All recent popes have changed the rules governing the choice of their successor, except for John Paul I, whose death on September 29, 1978 left him no time to reform the system during his 33-day papacy.
Pope Benedict XVI, who announced on Monday he would resign, altered the rules for the choice of his successor to ensure that the new pontiff enjoys as widespread support as possible.
Under the change, the new pope will have to be elected with a two-thirds majority, however many rounds of voting the process might take.
In a "motu proprio", or personal decree, Benedict XVI reversed a measure adopted in 1996 by his predecessor John Paul II in an "apostolic constitution".
Here is a factfile on how popes are chosen:
--In 1970 Pope Paul VI determined that the college of cardinals was to be limited to 120, with a maximum age of 80. He also ordered measures to prevent bugging of the proceedings.
--During the interregnum, the cardinal camerlengo is temporary head of the Roman Catholic church.
If the outgoing pope has died, the camerlengo arranges the funeral and burial of the deceased pope and organises the election of his successor, assisted by three cardinals who are elected by the college of cardinals, with three new cardinals elected every three days.
--The electoral conclave must meet at least 15 days, but no more than 20 days, after the pope´s death or resignation. The cardinals must take an oath of secrecy when they enter the conclave. The penalty for breaking the oath is automatic excommunication.
--Since 1271, when, following a deadlock, the cardinals were locked up and given only bread and water as a means of inducing them to draw the proceedings to a close, they have been required to remain in total isolation during the deliberations, with only a doctor and a cook to assist them.
--The vote is by secret ballot. Cardinals are not allowed to vote for themselves. Four ballots are held each day, two in the morning and two in the evening, until a result is obtained. The ballot papers are burnt after each count. If a new pope has been elected, the papers are burned with a substance that gives off white smoke, to signal the news to the waiting crowds outside. If no candidate has succeeded in gaining the necessary two-thirds majority, the smoke given off is black.
--Once a cardinal has been chosen, he is asked if he agrees to become pope and what name he wishes to be known by. Once he has done this, he immediately becomes Pontifex Maximus, the Holy Roman Pontiff.
--The dean of the college of cardinals then steps on to the main balcony of the Vatican and declares to the world: "Habemus Papam!" "We have a Pope!" The new pope then appears on the balcony and delivers his apostolic blessing.