Pope Benedict urged the young people to cherish their freedoms
Pope Benedict XVI has spoken out for the first time about growing up under the "monster" of Nazism.
Speaking at a youth rally in New York, he said his teenage years had been "marred by a sinister regime".
The Pope was a Hitler Youth member as a teen, usual for young Germans at the time, and was conscripted by the German army near the end of World War II.
Earlier, during a Mass at St Patrick's Cathedral in Manhattan he again condemned paedophile Catholic priests.
Pope Benedict's tour of the US is his first visit to the country since being elected head of the Catholic Church - it was the third anniversary of his elevation to the papacy on Saturday and the event was formally commemorated with the Mass at St Patrick's.
Prisoner of war
Later in the day he addressed a cheering crowd of 30,000 young people on the field of St Joseph's Seminary, in the New York suburb of Yonkers.
Let us thank God that so many people of your generation are able to enjoy the liberties which have arisen from the extension of democracy and respect for human rights
As a teenager, the pope was forced to join the Hitler Youth and he was conscripted into the German army towards the end of World War II, serving briefly in an anti-aircraft corps.
He deserted the German army towards the end of the war and was briefly held as a prisoner of war by the Allies in 1945.
After his release he studied theology and became a priest.
The Pope told the crowd his own years as a teenager had been "marred by a sinister regime that thought it had all the answers".
"Its influence grew, infiltrating schools and civic bodies, as well as politics and even religion, before it was fully recognised for the monster it was," he said.
"It banished God and thus became impervious to anything true and good.
"Let us thank God that so many people of your generation are able to enjoy the liberties which have arisen from the extension of democracy and respect for human rights."
Pope Benedict XVI on life in Germany as a teenager
At the earlier Mass at St Patrick's Cathedral, Pope Benedict was greeted by the Mayor of New York, Michael Bloomberg, and the cathedral was filled with priests, deacons and members of religious orders.
A choir sang as the Pope walked down the large cathedral's central aisle. The congregation rose and applauded and some people leaned over to touch his robe or kiss his Fisherman's Ring.
"I join you in praying that this will be a time of purification for each and every particular Church and religious community, a time for healing," the Pope said in his sermon, referring to the scandal of sexual abuse of children by Catholic clergy.
"I also encourage you to co-operate with your bishops who continue to work to effectively resolve this issue."
More than 4,000 US Catholic clergy have been accused of sexually abusing minors since 1950.
The Church has paid out more than $2bn (£1bn) in compensation and legal fees, most of it since the scandal erupted in 2002.
15 Apr: Arrived at Andrews Air Force Base
16 Apr: White House luncheon; talks with Mr Bush. Meeting with US bishops and prayer service in Washington (evening)
17 Apr: Washington Mass; addressed Catholic University; interfaith meeting
Speaking out on the issue again during the Mass at St Patrick's, the Pope said the scandal had not only caused much damage to the victims of paedophile abuse, but had diminished the reputation of the church in US society.
"A society which seems to have forgotten God and to resent even the most elementary demands of Christian morality," he said .
The Vatican official in charge of reviewing sexual abuse claims against clergy worldwide said on Friday that the Church was considering changes to canon law governing the handling of such cases.
The official, Cardinal William Levada, did not specify the changes but said they would make it easier to remove clergy who had sexually abused children.
The sexual abuse scandal has been a recurring theme in the Pope's visit.
Addressing 40,000 people at a Washington stadium earlier in the week, he spoke of the issue before talking privately to a group of people who had been abused by priests.
On Sunday, he will lead prayers at the scene of the 9/11 attacks in New York and then celebrate Mass at Yankee Stadium before returning to Rome later on Sunday.
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