Warning as Cardinals begin debate

The process of choosing a pope began today with a warning that the successful candidate must defend traditional teachings and reject attempts to modernise doctrine.

The call came from Cardinal Joseph Ratzinger, 78, known as "God's Rottweiler" for his conservative views and seen by some as a front runner to replace John Paul II.

A total of 115 cardinals were locked in conclave at the Sistine Chapel this afternoon.

In a sermon beforehand, Cardinal Ratzinger told the cardinals that the faith of many Christians had been shaken "by so many currents, ideologies and different ways of thinking". He said the Catholic Church faced an uncertain future threatened by the rise of Christian sects around the world.

He said the Church had to reject "a dictatorship of relativism" that denied the existence of absolute truths, adding: "An adult faith is not one that follows tides of trends and the latest novelties. To be adult and mature the faith must be deeply rooted in friendship with Christ."

Since John Paul's death on 2 April bookmakers have tipped Cardinal Ratzinger to succeed him. But some Vatican experts doubt that the German, whose dogmatic approach has polarised the Catholic world, will get the two-thirds majority needed to become pope.

In papal conclaves, like longdistance races, it is considered a disadvantage to break from the pack too early. The cardinals will emerge only when they have chosen the first new pontiff of the third Christian millennium and the 264th successor to St Peter. Black smoke from a chimney in the Sistine Chapel will mark an inconclusive vote. White smoke and the tolling of St Peter's bells will mark the election of a new pope.