VATICAN CITY, July 10, 2008 (AFP) - Pope Benedict XVI will head to Australia Saturday to meet hundreds of thousands of young people celebrating the Catholic Church's World Youth Day.

Young people from around the world are expected in Sydney for the event, aimed at portraying the Roman Catholic Church as a youthful, global and enthusiastic community.

'I am sure that from every corner of the Earth, Catholics will unite with me and the youths gathered (in Sydney) to invoke the Holy Spirit... in a variety of languages and cultures,' Benedict said during his Angelus prayer at the weekend.

Ahead of his longest journey since becoming pope three years ago, the 81-year-old Benedict urged the entire Church to feel a part of 'this new phase of the great youth pilgrimage across the world begun in 1985 by (his predecessor) John Paul II.'

His first public appearance will be at the head of a Sydney Harbour flotilla on July 17 and the trip will culminate in an open-air mass at Sydney's Randwick Racecourse expected to attract hundreds of thousands of pilgrims on July 20.

Ahead of the trip, Benedict's ninth outside Italy, Vatican officials have noted Australia's secular nature.

'Australia is a nation continent that has been strongly secularised, and where Catholics are a minority,' the Vatican's Youth Day pointman Cardinal Stanislaw Rylko said recently.

Benedict, the spiritual leader of the world's 1.1 billion Catholics, frequently criticises what he describes as the secularism of post-modern societies such as Australia, Europe and North America, saying they have lost a sense of 'transcendancy.'

Sydney Archbishop George Pell told Vatican Radio that while there was 'less hostility' to the Roman Catholic Church in Australia than in the United States, there was also 'less enthusiasm'.

'For us, indifference is the problem,' he said.

As he did during his US trip, Benedict is expected to offer apologies to Australian victims of sexual abuse by priests.

Australian bishops issued an apology for past abuses in 2002 and Pell made it clear that papal comments on the issue would be 'a welcome contribution.'

'I think it would be appropriate for the Pope to say something on that score,' he said.

The situation of Australia's still struggling Aborigines -- championed by John Paul II during his 1986 visit -- will also be part of Benedict's visit.

He is expected to address the issue during the July 17 welcome ceremony, when Aboriginal dancers and singers will take centre stage.

The aged German pontiff will spend the first four days of his visit recovering from the long flight from Rome at a retreat run by the conservative Catholic group Opus Dei in Sydney's northwestern outskirts.