Pope Francis has promised "solutions" to the issue of priestly celibacy in an interview that raises the possibility the Roman Catholic Church could eventually lift the interdiction on married priests.

In an interview with Italy's La Repubblica daily published on Sunday, Francis also condemned child sex abuse as a "leprosy" in the Church and cited his aides as saying that "the level of paedophilia in the Church is at two percent".

"That two percent includes priests and even bishops and cardinals," he said.

Asked whether priests might one day be allowed to marry, Francis pointed out that celibacy was instituted "900 years after Our Lord's death" and that clerics can marry in some Eastern Churches under Vatican tutelage.

"There definitely is a problem but it is not a major one. This needs time but there are solutions and I will find them," Francis said, without giving further details.

The interview was the third in a series with the 90-year-old founder of the La Repubblica daily, Eugenio Scalfari, a famous journalist and known atheist.

Francis begs forgiveness

Earlier this month Francis begged for forgiveness in his first meeting with Catholics sexually abused by members of the clergy and went further than any of his predecessors by vowing to hold bishops accountable for their handling of paedophile priests.

Abuse victims and their advocates had long demanded that higher-ups be made to answer for the decades-long cover-ups of rape and molestation of youngsters in a scandal that has rocked the church and dismayed its worldwide flock of 1.2 billion.

The pope celebrated a private Mass with six victims - two each from Ireland, Britain and Germany - at his Vatican residence, and spent the rest of the morning listening to their accounts, one-on-one.

"Before God and his people, I express my sorrow for the sins and grave crimes of clerical sexual abuse committed against you. And I humbly ask forgiveness," Francis said, according to the Associated Press news agency.

"I beg your forgiveness, too, for the sins of omission on the part of church leaders who did not respond adequately to reports of abuse made by family members, as well as by abuse victims themselves," the pope said.

"This led to even greater suffering on the part of those who were abused, and it endangered other minors who were at risk."