VATICAN CITY — In parts of the vast Catholic world, some bishops view clerical sexual abuse as more of a sin than a crime. Others attribute it to homosexuality or question that it exists at all. Where Catholics are a minority, as in the Middle East, reporting a pedophile priest to the civil authorities is tantamount to sentencing him to death.

As Pope Francis convenes church leaders for a meeting at the Vatican starting on Thursday to address the scourge of clerical sexual abuse, victims’ advocates are demanding urgent and uniform church laws to impose zero tolerance for priests who abuse minors and for the bishops who cover up for them, regardless of the culture in which they operate.

But Vatican officials say such a demand reflects a misconception that change in a global and ancient institution can be made with the wave of a papal wand.

The diversity of legal and cultural barriers to identifying abusers and assisting victims, as well as entrenched denial, makes putting in place one world standard virtually impossible, they say.