VATICAN CITY (Reuters) - Jewish leaders reacted with dismay on Sunday to comments in Pope Benedict's new book that his wartime predecessor Pius was a "great, righteous" man who "saved more Jews than anyone else."

Many Jews accuse Pius, who reigned from 1939 to 1958, of having turned a blind eye to the Holocaust. The Vatican says he worked quietly behind the scenes because speaking out would have prompted Nazi reprisals against Catholics and Jews in Europe.

In his book to be published on Tuesday, called "Light of the World: The Pope, the Church, and the Sign of the Times," the German pope says Pius did what he could and did not protest more clearly because he feared the consequences.

In the book-length interview with a German journalist, the pope says of Pius:

"The decisive thing is what he did and what he tried to do, and on that score we really must acknowledge, I believe, that he was one of the great righteous men and that he saved more Jews than anyone else."

Jewish leaders said they were surprised by the comments.

"Pope Benedict's comments fill us with pain and sadness and cast a menacing shadow on Vatican-Jewish relations," said Elan Steinberg, vice president of the American Gathering of Holocaust Survivors and their Descendants.

"The assertion that Pius saved more Jews than anyone else during the Holocaust is categorically contradicted by the known historical record. As survivors of the Holocaust we have a solemn obligation to the memory of those murdered to defend the truth of the tragedy till our last breath," he said.

When the pope visited Rome's synagogue in January, the leader of the city's Jewish community told him bluntly that Pius should have spoken out more forcefully against the Holocaust to show solidarity with Jews being led to the Auschwitz death camp.

NEW TENSIONS

Pius, including the possibility that the Vatican may one day make him a saint, is one of the main points of contention in relations between Jews and the Vatican. The pope's latest comments raised new tensions.

"The Shoah represents the darkest abyss of our history and perhaps of human history," said Rabbi David Rosen, International Director of Interreligious Affairs of the American Jewish Committee, using the Hebrew word for the Holocaust.

"How can one say that any persons did all they could have done in the face of such evil unless they laid down their life to oppose it?"

Last December, Benedict took the decision to advance Pius XII on the path towards sainthood by recognising his "heroic virtues," a move that almost led to the cancellation of the synagogue visit.

In the book, Benedict says he took the decision after an inspection of unpublished archival records in the Vatican but acknowledged that it was impossible to evaluate the hundreds of thousands of documents in a rigorously scientific manner.

"It is distressing that the pope has found it necessary to come to judgement on Pope Pius XII as he himself admits that the files and archives are not available to make a full judgement," said Abe Foxman, national director of the Anti-Defamation League in the United States.

Jews have asked that the process that could lead to making Pius a saint be frozen until after all the Vatican archives from the period are opened and studied.

"There is certainly enough evidence to refute those who charge that Pius XII stood idly by while the lives of Jews and others were imperilled," said Rosen, who is based in Jerusalem.

"On the other hand it appears that he never directly -- certainly not publicly -- challenged the Nazi regime regarding the extermination of the Jews; and arguably even more dramatic, never made any mention of this, let alone any expression of regret, subsequent to World War Two," he said.

(Writing by Philip Pullella; Editing by Peter Graff)