Pope Benedict XVI on Sunday implored Christians to mend their divisions which he described as “an insult to God”.
On a week of prayers dedicated to Christian unity, the pontiff called for a “serious effort to convert to Christ” during Sunday's prayer.
“Each division of the Church is an insult to God,” he said, speaking from his apartment's balcony on Saint Peter's Square.
Earlier this week he expressed “deep regret over the impossibility of sharing the same Eucharist (Holy Communion), a sign that we are still far from reaching unity”.
He also highlighted the hardships Christians face in the Middle East, a reference to recent attacks, including the deadly bombing of a Coptic Church in Egypt that killed 21 people.
Threatening to exacerbate tensions between Muslims and Egypt's minority Christians, a suicide bomber killed 21 people outside a church in the northern city of Alexandria after a New Year's Eve mass at the start of 2011.
“We know the hardships our brothers and sisters have to face in the Holy Land and the Middle East...sometimes to the point of sacrificing their lives,” he said.
Earlier this month the pope called on the Arab world to protect Christians, prompting Egypt to recall its ambassador and slam the comments as “unacceptable interference”.
And the imams of Al-Azhar in Egypt, the largest centre for Sunni Islam close to Cairo, suspended relations with the Vatican, saying Pope Benedict XVI's comments were an “attack on Islam”.