Pope Benedict XVI to resign

June 16, 2010: Pope Benedict XVI leaving at the end of his weekly general audience in St. Peter's Square, at the Vatican. (AP)

April 19, 2005: Pope Benedict XVI greeting the crowd from the central balcony of St. Peter's Basilica moments after being elected, at the Vatican. On Monday, Benedict XVI announced he would resign Feb. 28, the first pontiff to do so in nearly 600 years. The decision sets the stage for a conclave to elect a new pope before the end of March. (AP)

April 19, 2005: Pope Benedict XVI greeting the crowd from the central balcony of St. Peter's Basilica moments after being elected, at the Vatican. (AP)

Nov. 26, 2011: Pope Benedict XVI waving as he leaves Paul VI hall after attending a concert of the Asturias Principality Symphony Orchestra directed by Chilean conductor Maximiano Valdes at the Vatican. (AP)

May 25, 2006: Pope Benedict XVI lifting his scull cap during an ecumenical meeting at the Holy Trinity church in Warsaw, Poland. (AP)

Feb. 10, 2013: Pope Benedict XVI blesses the faithful from his studio's window overlooking St. Peter's square during the Angelus noon prayer, at the Vatican. (AP)

Feb. 9, 2013: Pope Benedict XVI is greeted by Grand Master of the Knights of Malta Matthew Festing at the end of a mass celebrated by Cardinal Tarcisio Bertone, not pictured, to mark the 900th anniversary of the Order of the Knights of Malta in St. Peter's Basilica at the Vatican. (AP)

Feb. 2, 2013: Pope Benedict XVI celebrates a mass for priests and nuns in St. Peter's Basilica at the Vatican. (AP)

April 9, 2009 FILE photo, Pope Benedict XVI offers a nun the Holy Communion, a Chrism Mass inside St. Peter's Basilica at the Vatican, as Benedict XVI celebrated a Holy Thursday Mass that included the traditional blessing of holy oils. (AP)

Feb. 4, 2013: In this photo provided by the Vatican newspaper L'Osservatore Romano, Pope Benedict XVI meets the Chaldean Catholic Patriarch of Babylon and the Head of the Chaldean Catholic Church Louis Raphaël I Sako during a private audience at the Vatican. (AP)

April 28, 2009 FILE photo Pope Benedict XVI stands by the salvaged remains of Pope Celestine V, in the 13th-century Santa Maria di Collemaggio Basilica, the symbol of the Italian city of L'Aquila. Pope Celestine V, the 13th-century hermit and saint, was one of the earlier popes to resign. (AP)

May 12, 2009 FILE photo, Pope Benedict XVI places a note in the Western Wall, Judaism's holiest site, in Jerusalem's Old City. (AP)

Feb. 8, 2013: Pope Benedict XVI blesses faithful at the end of his visit at the Roman seminary in Rome. (AP)

Dec. 8, 2009 FILE photo ofPope Benedict XVI, waving from his popemobile on his way to the Spanish Steps in central Rome, for the traditional prayer before a statue of the Virgin Mary on the occasion of the Immaculate Conception. (AP)

July 10, 2009 FILE photo shows President Barack Obama and first lady Michelle Obama meeting with Pope Benedict XVI, at the Vatican. (AP)

March 25, 2012 FILE photo, Pope Benedict XVI waves from the popemobile wearing a Mexican sombrero as he arrives to give a Mass in Bicentennial Park near Silao, Mexico. (AP)

April 24, 2005 FILE photo shows thousands of people attending the installment Mass of Pope Benedict XVI in St. Peter's Square, at the Vatican. (AP)

April 24, 2005 FILE photo shows Pope Benedict XVI holding a cross as he celebrates his installment Mass in St. Peter's Square, at the Vatican. (AP)

April 24, 2005 FILE photo shows Pope Benedict XVI opening his arms as he celebrates his installment Mass in St. Peter's Square, at the Vatican. (AP)

Feb. 11, 2013 - Georg Ratzinger, brother of Pope Benedict XVI , sits in his house in Regensburg, southern Germany. The pope's 89-year-old brother told a German news agency that the pope has had difficulty walking recently and has considered stepping down for months. “His age is weighing on him,” Georg Ratzinger said. “At this age my brother wants more rest.” (AP)

Dec. 22, 2003 - FILE photo of late Pope John Paul II greeting then Cardinal Joseph Ratzinger, Prefect of the Catholic Church's Congregation for the Doctrine of the Faith. (AP)

1979 FILE - Pope John Paul II poses with Cardinal Joseph Ratzinger of Munich, who was named on Nov. 25, 1981, Prefect of the Congregation for the Doctrine of the Faith and President of the Pontifical Biblical Commission and of the International Theological Commission, the former Holy Office. Ratzinger was elected Pope, April 19, 2005. (AP)

September 1978 - FILE photo Albanian-born Mother Teresa, left, and German Cardinal Joseph Ratzinger, attend a Mass during the 85th German Catholics Day in Freiburg, southern Germany. (AP)

June 29, 1951: Pope Benedict XVI is pictured with fellow priests, his brother Georg Ratzinger and friend Rupert Berger on the day they were ordained into the priesthood in Munich, Germany. (Reuters)

June 29, 1951 - FILE photo of Joseph Ratzinger, right, and his brother Georg after their ordination to priesthood in Freising, southern Germany. (AP)