Pope Benedict says he will confer one of the Roman Catholic Church's highest honors on a 16th-century Spanish saint.

The leader of the world's 1.6 billion Catholics made the surprise announcement Saturday during a visit to the Spanish capital, Madrid.

The pontiff said he will declare St. John of Avila a doctor of the church. The title is reserved for figures of eminent doctrine and remarkable holiness. There are currently 33 such doctors in the church.

St. John of Avila, who lived from 1500-1569, is the patron saint of Spain's diocesan clergy and was considered one of the greatest preachers of his time.

Pope Benedict earlier warned against “false gods” as he celebrated mass in Madrid's Almudena Cathedral for 6,000 young men preparing to join the priesthood.

Later Saturday, the pope is to preside over a vigil service with the estimated 500,000 young people who have gathered for the weeklong religious festival that ends Sunday.