VATICAN CITY, Holy See -- Five conservative cardinals urged Pope Francis to reaffirm traditional Catholic doctrine in a document made public Monday, two days before a major gathering on the Church's future.

Pope Francis (AFP)

The cardinals, from four different continents, asked questions of the pontiff about the blessing of same-sex couples, the ordination of women and the conditions surrounding confession and absolution, according to the document seen by AFP.

In a seven-page response, the pontiff affirmed that while the "divine Revelation" was "immutable", the Church should be humble and recognize that she "needs to grow in her understanding."

Unsatisfied with this response, the five reformulated their questions -- entitled "Doubts" -- and published an open letter to Catholics, according to two specialist Vatican blogs that first revealed the existence of the cardinals' questions.

They wrote that their intention was to inform the faithful "so they are not subject to confusion, error and discouragement."

The five cardinals are Walter Brandmuller of Germany, Raymond Burke of the United States, Sandoval Iniguez of Mexico, Robert Sarah of Guinea and Joseph Zen of Hong Kong.

All are known for their conservative positions, and none currently hold office in the Vatican government.

Their challenge was made public ahead the opening Wednesday of the general assembly of the Synod of Bishops, a four-week assembly focused on the future of the Catholic Church.

Topics to be addressed include the place of LGBT+ people within the Church, whether women should be ordained deacons, and whether married men can serve as priests in regions with insufficient clergy.