Cardinal Emmanuel III Delly, the head of Iraq's largest Christian group, resigned on Wednesday, the Vatican said, announcing that a synod has been convoked for January to elect a successor for a community faced with religious persecution.

Delly, a simple man of faith who campaigned for peace between Muslims and the country's Christian minorities, had been Patriarch of the Chaldean Catholic Church since 2003 and resigned because he had reached the compulsory retirement age of 85.

The church has some 400,000 members in Iraq, though the numbers of faithful are constantly on the decline because of forced or voluntary emigration. It has around three million followers spread around the world.

Delly's successor will be elected on January 28 by a Synod of bishops of the Chaldean Church convened by Pope Benedict XVI, the Vatican said in a statement.

The meet will be headed up by Cardinal Leonardo Sandri, prefect of the Congregation for the Oriental Churches, who has just returned from a trip to Iraq in which he voiced the pope's solidarity with Christians under the threat of religious violence.

Sandri was present on Saturday at the consecration of a recently-restored church in Baghdad which was damaged in a bomb attack in 2010 which killed 52 people.

Delly, a shy man now in poor health, was appointed Cardinal by Benedict in 2007 at the age of 80, the first Chaldean Patriarch to receive the honor.

Born close to the northern Iraq city of Mosul in 1927, he became auxiliary bishop of Babylon in 1962.

He spent much of his time and energy trying to help Iraq Christians, fleeing the country because of persecution, find a safe refuge abroad.

The Chaldean flock he led has its roots in the Assyrian community and their liturgical language is the Aramaic once spoken by Jesus Christ.