The Pope has said he hopes it will "help in the process of repentance, healing and renewal".
The message is expected to express contrition for what he himself has already described as shameful and hateful behaviour by some priests.
It will include guidelines on preventing and punishing sexual abuse of children by priests.
Victims rights groups are demanding an assurance by the Pope that there will be no further cover ups by his bishops.
They also want a clear instruction that it is the responsibility of local church hierarchies to inform the police about cases of paedophilia by priests which come to their notice, as well as to report them back to Rome.
Cover ups
I have never seen a graver crisis affecting the very credibility of the leadership of the world's longest surviving international organisation, the Roman Catholic Church
Last year a damning report into child abuse in the Dublin archdiocese criticised the Catholic Church hierarchy for covering up hundreds of cases going back to the early 1970s.
But what was first perceived in Rome as a series of local scandals has now escalated into a worldwide problem for the Catholic Church with new allegations emerging each week from Catholics claiming they have been victims of sexual abuse by priests.
The Catholic Church is on the defensive, its reputation as a guardian of morality at risk, our correspondent says.
And there is the prospect of an avalanche of claims for compensation by victims, which could lead to financial ruin in some dioceses, as has already happened in the US, where the greatest number of cases has been reported.
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