A measure intended to promote greater unity within the Roman Catholic Church by increasing the use of the Latin Mass is sparking confusion and controversy among Jewish groups as they scramble to understand the full extent of the decision.

On Saturday, July 7, Pope Benedict XVI issued a Motu Proprio, literally a declaration in the pope’s own name, authorizing wider use of the Latin Mass, an older form of Catholic worship that includes a prayer read only on Good Friday for the conversion of the Jews. The pope removed a rule that had required a bishop’s permission before the Mass could be used in an individual church.

Reaction in the Jewish world was divided between those warning of possible setbacks in Jewish-Catholic relations and others saying clarification was needed from the Vatican before judging the pope’s declaration.

Leading the charge of those voicing alarm was the Anti-Defamation League, which even before the pope’s decision had been made public, issued a statement calling it a “body blow to Catholic-Jewish relations.”

The main question for Jewish organizations is whether the pope intends to permit churches to recite the conversion prayer on Good Friday.

Allowing the prayer to be read, Jewish communal officials said, would appear to run counter to the spirit of Nostra Aetate, the landmark 1965 Vatican declaration, and subsequent reforms that absolved Jews of responsibility for the killing of Jesus and laid the groundwork for four decades of improved Catholic-Jewish relations.

In particular, Jewish groups say that a prayer to convert the Jews would undermine previous steps taken by the church recognizing the validity of Judaism.

Some Jewish groups took a more cautious approach than the ADL, as they sought to gain a clearer understanding of the pope’s decision. In a letter to the Vatican’s point man on Jewish relations, Walter Cardinal Kasper, the International Jewish Committee on Interreligious Consultations sought clarification of the pope’s ruling.

Vatican observers broadly agree that reinstating the prayer for Jewish conversion is incidental to the pope’s larger goal, which the pontiff himself said was to come “to an interior reconciliation in the heart of the church.” The Latin Mass is seen as possessing a certain spiritual grandeur that some Catholics — even those who accept the wider reforms that did away with the Mass — have an emotional attachment to.

The problem, some Jewish observers said, is that on the surface it would seem that the Good Friday prayer runs counter to Nostra Aetate and other reforms.

“It is as if the document Nostra Aetate had never been promulgated and placed in the body of official Catholic teaching,” said Rabbi Gerald Meister, an adviser to the Israeli Foreign Ministry on Christian affairs.

Though praying for the conversion of the Jews represents “a rather primitive form of spiritual anti-Semitism,” Meister said, he added that he doubts that the prayer will be found in widespread use.

“If not, we will have to examine this further,” Meister said.

For their part, the bishops conference maintains that Nostra Aetate remains in force as the focal point for relations with the Jews. As to how the church reconciles the seeming contradiction, Father James Massa of the U.S. Conference of Catholic Bishops said that alternative understandings of the liturgy would likely be forthcoming from Catholic commentators.

“I think this document is going to be interpreted over the next few weeks,” Massa said. “I think we do owe an explanation as to what the Motu Proprio implies about the use of the 1962 Missal with respect to the Good Friday liturgy.”

Massa stressed that concern for the future of Catholic-Jewish relations are unfounded. “I firmly believe that our relationships with our Jewish partners are deep and abiding,” he said. “I think we will be able to weather the tensions that might arise from certain understandings of the Motu Proprio.”

The criticism of the Vatican by the ADL and its national director, Abraham Foxman, was assailed by conservative pundit Patrick Buchanan.

In an article published Tuesday on the conservative Web site Human Events, Buchanan challenged the ADL’s claim that it was “hurtful and insulting” for Catholics to pray for the conversion of Jews.

“What is Abe talking about?” wrote Buchanan, an erstwhile presidential candidate. “Indeed, if one believes, as devout Catholics do, that Christ and his Church hold the keys to the Kingdom of Heaven, it would be anti-Semitic not to pray for the conversation of the Jews.”