Pope Benedict XVI has told American Jewish leaders that any denial of the Holocaust is "intolerable", especially if it comes from a clergyman.
He was speaking at the Vatican at his first direct talks with Jewish leaders since he lifted the excommunication of a Holocaust-denying bishop.
The Jewish leaders appeared to be divided over the pontiff's stance.
The Pope has said he was unaware that Bishop Richard Williamson had denied the full extent of the Holocaust.
During the meeting, he confirmed he was planning to visit Israel.
Vatican sources have said the trip is scheduled for May.
The Pope told about 60 delegates from the Conference of American Jewish Organisations that "any denial or minimisation of this terrible crime [was] intolerable", especially from a priest.
"The hatred and contempt for men, women and children that was manifested in the Shoah [Holocaust] was a crime against humanity," he said.
"This should be clear to everyone, especially to those standing in the tradition of the Holy Scriptures..."
Pope Benedict admitted that the 2,000-year-old relationship between Judaism and the Church had passed through some painful phases.
But he repeated the prayer the late Pope John Paul made when he visited Jerusalem in 2000, pleading for forgiveness from Jews for Christians who had persecuted them throughout history.
In response, Rabbi Marc Schneier, head of the American Jewish congress, said his community had faced "painful and difficult days" because of Bishop Williamson's comments.
"Thank you for your understanding of our pain and anguish and your firm statement expressing unquestioned solidarity with the Jewish people," he said.
The Jewish leader added that Jews faced a "new scourge of anti-Semitism" including the desecration and burning of synagogues.
However, Abraham Foxman, another Jewish leader, said after the meeting that the Vatican had to excommunicate Bishop Williamson because "every moment that he stays in the Church gives him credibility".
"Today's statement was important but it did not bring closure," he added.
Catholic-Jewish relations have soured over the Pope's decision last month to lift the excommunication of Bishop Williamson.
The Jewish leaders had made it clear before the meeting that they were expecting the Pope to announce he was breaking all ties with Bishop Williamson's traditionalist group of Catholics until they recanted their anti-Semitic views, the BBC's David Willey reports from Rome.
But the Pope made no specific mention of the row during his address, our correspondent notes.
Bishop Williamson was among four ultraconservative bishops - all members of the traditionalist Society of St Pius X (SSPX) - whose excommunications were lifted, in a bid by the Pope to end a schism that began in 1988 when they were ordained without Vatican permission.
But it was then revealed that Bishop Williamson, who was born in Britain, had given an interview to a Swedish television programme last November, in which he disputed that six million Jews had died at the hands of the Nazis, and said that none had died in gas chambers.
Bishop Williamson, who has been removed from his post as the head of a seminary in Argentina, has refused to recant his remarks, despite an order from the Vatican to do so - merely saying he will re-examine the evidence on the Holocaust.
The Pope said previously he had not known about Bishop Williamson's views - a stance that Elena Curti, deputy editor of the Tablet Catholic newspaper, told the BBC was "extraordinary".
They were "well known, it seems, to virtually everybody else", she said.