VATICAN CITY -- Pope Benedict XVI on Thursday backed the beatification of his controversial World War II predecessor Pius XII, defending his actions during a "complex historical moment."

Benedict said Pius "often acted in secret and in silence" but spared no effort in "the defense of the persecuted, with no distinction of religion, ethnicity, nationality or political affiliation."

Celebrating a mass commemorating 50 years since the death of the wartime pope, the 81-year-old pontiff said: "In light of the real situations of this complex historical moment, he sensed that this was the only way to avoid the worst and save the greatest possible number of Jews."

He said in his homily: "As we pray that the process of beatification of servant of God Pius XII proceeds happily, it is well to recall that holiness was his ideal, an ideal that he constantly urged for all."

The process of beatifying Pius XII, which was launched in 1967 and is approaching completion, would place the pope accused of remaining silent during the Holocaust one step away from sainthood.

It has sparked bitter debate and tension between Catholics and Jews, and last year Benedict created a special commission to study the issue.

On Thursday, Benedict did not indicate when he would sign a decree attesting to the "heroic virtues" cited in Pius XII's beatification dossier, currently on his desk.

"The pope has not yet signed this decree, considering that a time for reflection would be appropriate," said Vatican spokesman Federico Lombardi.

Just three days ago, the Grand Rabbi of Haifa, Israel, spoke out against such an honor for the late pope.

Shear-Yushuv Cohen, who on Monday became the first Jew to address a synod of bishops at the Vatican, said Pius XII "should not be seen as a model and he should not be beatified because he did not raise his voice against the Holocaust."

On Tuesday one of the Vatican's most senior cardinals defended the wartime record of Pius XII, who was pope from 1939 until his death on October 9, 1958.

Secretary of State Tarcisio Bertone wrote in the Vatican newspaper, Osservatore Romano, that if Pius XII "had intervened publicly, he would have endangered the lives of thousands of Jews who, at his request, were hidden in the 155 convents and monasteries in the city of Rome alone."

The Vatican paper was quoting from the preface to a forthcoming book on Pius XII, in which the cardinal argued that it was "profoundly unjust" to attack Pius XII over his wartime position, "forgetting not only the historical context but also his immense charity work" for Jews.

Benedict asked in his homily: "And how can one forget the message over national radio in December 1942? With a voice choked with emotion he deplored the situation of 'hundreds of thousands of people who ... at times only for reasons of nationality or parentage are destined to death'."

This was "a clear reference to the deportation and the extermination perpetrated against the Jews," Benedict said.