Pope Benedict XVI has promised his "unconditional reverence and obedience" to his successor in his final words to his cardinals, a poignant farewell before he becomes the first pope in 600 years to resign.
The pontiff appeared to be trying to defuse concerns about possible conflicts arising from the peculiar situation of having a reigning pope and a retired one.
Delivering an unexpected speech today, Benedict also urged the "princes" of the church to set aside their differences as they elect the next pope, urging them to be unified so that the College of Cardinals works "like an orchestra" where "agreement and harmony" can be reached despite diversity.
He said he would pray for the cardinals in coming days as they choose his successor.
"Among you is also the future pope, whom I promise my unconditional reverence and obedience," Benedict said in his final audience.
Benedict's decision to live at the Vatican in retirement, be called "emeritus pope" and "Your Holiness" and to wear the white cassock associated with the papacy has deepened concerns about the shadow he will cast over the next papacy.
But Benedict has tried to address those worries, saying that once retired he would be "hidden from the world."
In his final speech in St Peter's Square yesterday, he said he wasn't returning to private life, but rather to a new form of service to the church through prayer.
Shortly before 5 pm, Benedict will leave the palace for the last time as pontiff, head to the helipad at the top of the hill in the Vatican gardens and fly to the papal retreat at Castel Gandolfo south of Rome.
There, at 8 pm sharp, Benedict will become the first pontiff in 600 years to resign. The doors of the palazzo will shut and the Swiss Guards will go off duty, their service protecting the head of the Catholic Church over - for now.
Who will succeed Benedict?
Here are some of the possible contenders to replace Pope Benedict XVI, who resigns today as pontiff, the first to do so for nearly 600 years.
Cardinal Marc Ouellet, 68, the Canadian head of the Vatican's office for bishops.
Archbishop of Quebec between 2003 and 2010, he spent 10 years as a missionary priest in Colombia, and is fluent in a range of languages. He is known as a strong defender of orthodoxy and is said to come from the same school of theological thought as Pope Benedict.
Cardinal Gianfranco Ravasi, 70, president of the Pontifical Council for Culture.
A former academic theologian and Biblical scholar, he is noted for his work encouraging dialogue between believers and non-believers and his "outreach" to science. He was chosen this year by Pope Benedict to lead the Vatican's Lenten spiritual retreat - a papal favour which could mark him out as a frontrunner.
:: Cardinal Leonardo Sandri, 69, an Argentinian and prefect of the Congregation for the Oriental Churches.
A "consummate" Vatican insider and viewed as a pair of "safe hands", he announced Pope John Paul II's death to the world on April 2, 2005, saying: "We all feel like orphans this evening."
His experience as head of the Congregation for the Oriental Churches is said to have given him a special understanding of the experience of Christians in the Middle East including the plight of the Christian population in Iraq following the war in 2003.
:: Cardinal Odilo Scherer, 63, Archbishop of Sao Paolo in Brazil.
He is head of the largest diocese in the world's largest Catholic country and spent several years working at the congregation for bishops at the Vatican. A German Brazilian by birth, he is seen as the strongest Latin American candidate.
:: Cardinal Christoph Schonborn, 68, Archbishop of Vienna.
An intellectual and a scholar who studied under Pope Benedict and is close to the outgoing pope. He is currently dealing with a rebellion in Austria by Catholics who are calling for reform of the Church in areas such as priestly celibacy and the role of women. The cardinals may not want to elect two German-speaking popes in a row.
:: Cardinal Angelo Scola, 71, Archbishop of Milan.
Cardinal Scola was said to have been "papabile" - a possible contender for pope - during the conclave to replace Pope John Paul II in 2005, and is an influential philosopher and theologian.
He is a member of the powerful Congregation for the Doctrine of the Faith (CDF), responsible for ensuring Catholic orthodoxy.
:: Cardinal Luis Tagle, 55, Archbishop of Manila, Philippines.
Highly praised and described by Vatican commentator John Allen as a "genuine intellectual with a common touch". He is seen as an outside chance to be elected because he is considered too young. If elected at 55, he could be pope for more than 30 years.
:: Cardinal Peter Turkson, 64, from Ghana, president of the Pontifical Council for Justice and Peace.
Charismatic and approachable, Cardinal Turkson is a popular figure and would be the first pope from Africa since Gelasius I more than 1,500 years ago.
But the department he heads is not powerful within the Roman curia, and he has raised eyebrows by his willingness to discuss his chances of becoming pope. He is also seen by some as being gaffe-prone.
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