Pope Benedict's view that there might be rare cases where condom use is acceptable comes at a time when the Catholic church's image in Europe has been battered by child abuse scandals.
Today's revelation that a Minnesota priest charged in a 2007 sex abuse case involving a teenage girl still practices in India continues to put a spotlight on the Vatican and Pope Benedict.
Investigations into charges of sexual and physical abuse of children by German Catholic priests are getting under way, and involve a choir run by Pope Benedict's brother. Did the pontiff know about the allegations when he was a bishop in his home country? "We do not know," a German Catholic church spokesman said.
The Vatican is trying to clarify efforts to reconcile with a sharply right-wing set of bishops excommunicated in 1988.
The gathering follows a successful Muslim-Catholic forum at the Vatican.
Preaching universal values at the UN, Benedict will urge followers to strengthen their Catholic identity.