Pope Benedict today said Christians and Jews must join forces so the "insane racist ideology" that led to the Holocaust never resurfaces.
Making a historic visit to a synagogue once destroyed by the Nazis, the Pope paused to pray at a memorial to the six million killed as he began the landmark visit.
The German Pope listened as Rabbi Netanel Teitelbaum intoned the Kaddish, the Jewish prayer for the dead, and the sound of the blowing of the Schofar, a ram's horn, filled the temple. Pope Benedict is only the second Pope known to have visited a synagogue.
The first was John Paul, who visited a Rome synagogue in 1986.
Speaking in the temple destroyed by the Nazis during the anti-Jewish Kristallnacht attacks in 1938 and rebuilt in 1959, the Pope called the Holocaust "this unspeakable and previously unimaginable crime.
"In the 20th century, in the darkest period of German and European history, an insane racist ideology, born of neo-paganism, gave rise to the attempt, planned and systematically carried out by the regime, to exterminate European Jewry," he said.
Although Catholic-Jewish relations have improved greatly in the past half-century, particularly during the 27-year reign of John Paul II, Pope Benedict warned that new threats of racism and anti-Semitism were always lurking.
"It is a particularly important task, since today, sadly, we are witnessing the rise of new signs of anti-Semitism and various forms of a general hostility towards foreigners," he said.
"The Catholic Church is committed - I reaffirm this again today - to tolerance, respect, friendship and peace between all peoples, cultures and religions," he said.
He also urged both sides to try to reach what he called "a shared interpretation of disputed historical questions."
This appeared to be reference to the role of wartime pontiff Pius XII. Many Jews say that pope, who reigned from 1939 to 1958, turned a blind eye to the Holocaust. The Vatican says he worked behind the scenes to save Jews and did not speak out more forcefully for fear of instigating Nazi reprisals.
Pope Benedict
served briefly in the Hitler Youth during the war when membership of the Nazi paramilitary organisation was compulsory.