World Catholic leader Pope Leo XIV on Tuesday appealed to a group of ultra-traditionalist Catholics not to go ahead with its planned consecration of bishops on Wednesday, an act that could lead to a full schism with the Vatican.

The group, the Society of St. Pius X (SSPX), was founded in 1970 by Catholics who opposed the liberal reforms to the church introduced by the 1960s Second Vatican Council.

What did the pope say about the planned consecration?

"I plead with you and ask you with all my heart: Please turn back!” Leo wrote in a letter to the Rev. Davide Pagliarani, the superior of the Society of St. Pius X, calling the plan a schismatic act and a "sin of extreme gravity."

In the letter, the pontiff repeated that the Vatican was prepared to enter into a dialogue and warned of negative impacts for those involved.