Pope Benedict XVI on Wednesday left for his first official trip to the Americas where the Roman Catholic Church faces increasing competition from evangelical faiths.
During a four-day stay in Brazil, the pope will open a conference of Latin American bishops where the shrinking number of Catholics in its stronghold region will be a key topic.
South America is home to nearly half of the world's 1.1 billion Roman Catholics. But in Brazil, while 64 percent of the population is Catholic, the figure has fallen from 74 percent a decade ago, according to a recent study.
The number of Pentecostal evangelicals has risen to 17 percent from 11 percent, said the Datafolha study based on 44,642 interviews.
On Thursday, Pope Bendict is to meet young people in Sao Paulo's Pacaembu stadium. On Friday, hundreds of thousands of people are expected to attend a special mass for the canonisation of Brother Galvao, Brazil's first saint.
The friar, who lived from 1739 to 1822, founded monasteries and convents throughout Brazil but is best known today because of his reputed healing powers.
After the mass, the pope will fly to Aparecida, a shrine dedicated to the cult of Our Lady of the Apparition, the patron saint of Brazil, where on Sunday he will open the fifth assembly of the episcopal conference of Latin America and the Caribbean.
The conference of 166 bishops and cardinals from the 22 countries of Latin America and the Caribbean will meet for two weeks.
It will be its first meeting in 15 years and highlights the growing faith crisis.
Pope Benedict has been preparing this trip for many months with Latin American bishops, and as part of the campaign is expected to highlight the importance of the family in Latin American life.
But the Roman Catholic church lost a key social battle last month when Mexico City, an important Catholic bastion, decriminalised abortion.
Brazilian prelate Claudio Hummes, archbishop of Sao Paulo, raised the alarm about declining church numbers in October 2005, asking: "How much longer will Latin America still be a Catholic continent?"
Latin America has a severe shortage of Catholic priests, with an average of 7,500 faithful per priest compared with the world average of 2,677, according to Vatican figures.
Analysts say the 80-year-old pope, who is scheduled to arrive in Sao Paolo at 1930 GMT, will use his trip to Brazil to promote Christ's divinity over the politicized Jesus embraced by Latin America's liberation theologists.
Benedict is said to be convinced that the struggle for influence with evangelical sects revolves around the image of Christianity's central figure, the subject of his just-published book "Jesus of Nazareth."
However the head of the Roman Catholic Church argues that the pentecostal trend has little to do with liberation theology, the movement with Marxist overtones that swept the Latin American region, especially Brazil, in the 1970s.
As cardinal Joseph Ratzinger, when he headed the Vatican's doctrinal enforcement body for 24 years, the pope spearheaded opposition to liberation theology, notably condemning Brazilian proponent Leonardo Boff in 1985.
