Few expected Pope Benedict to reach out to other Christian churches aggressively when he was elected in April 2005. Yet the rise of secularism among European Christians and the expansion of Islam on the Continent in recent decades have influenced thinking within Vatican corridors. In addition, this pope considers divisions among rival Christian churches as a threat to Roman Catholicism's credibility in the market of ideas and faiths, according to Vatican analysts and advisers to the pope.

"Anyone who thought he wasn't serious about ecumenical dialogue was seriously mistaken," said the Rev. Joseph Fessio, one of Pope Benedict's former students whom he occasionally consults.

Yet some Christians don't view Pope Benedict's latest move as an ecumenical gesture, and they warn that it risks derailing decades of formal dialogue between the Vatican and Anglican leaders.

Much of Pope Benedict's reputation as a hard-liner stems from his days as Cardinal Joseph Ratzinger, the late pope John Paul II's chief enforcer of doctrine. Over two decades, the then-cardinal addressed controversial issues ranging from bioethics to birth control. While some other Christian churches began to ordain women, the Catholic Church resisted.

Some of his most contentious positions addressed the question of how the Catholic Church relates to other faiths and Christian denominations.

In 2000, his office issued the document "Dominus Iesus," which outraged leaders of other religions and Christian churches by asserting the Catholic Church was the only sure path to salvation.

The document also said that divisions among Christian churches were undercutting the mission of Roman Catholicism as the universal church. But that message was obscured by the document's confrontational tone, Vatican analysts say.

For decades, Catholic officials have engaged in talks with other Christian leaders with the aim of reaching compromises on doctrine. At the same time, Pope Benedict has said each church needs to defend its own doctrine, and rival Christian churches need to accept each others' differences.

Pope Benedict signaled his intentions on the Vatican's ecumenical approach early in his pontificate. In one of his first Masses as pope, the pontiff said he planned to make ecumenical dialogue his "primary task."

He also has reached out to other religions, meeting with Muslim leaders in Turkey and paying a visit to the Holocaust memorial Yad Vashem in Israel.

There still are few details on the new Apostolic Constitution that amends church laws to attract Anglicans. The new laws will create church structures, called personal ordinariates, that will operate within local Catholic dioceses and be administered by former Anglican clergy who convert to Catholicism.

The ordinariates will allow Anglicans to enter into full communion with the pope while continuing to practice a large part of their traditional liturgy, according to Vatican officials. The new structures also will recognize the ordinations of Anglican priests, including those who are married.

But the Vatican hasn't released the text of the new regulations that will govern how the ordinariates will function, leaving many Anglicans to question whether the pope is genuinely carving out a space for Anglicanism within the Catholic Church.

Some Anglican bishops have expressed concern over whether the proposed system will actually allow those who convert to keep their Anglican practices. One point of concern is that the Vatican has said that married former Anglican priests will never be able to become a Catholic bishop.

The Rt. Rev. Michael Nazir-Ali, a married Anglican cleric who is bishop of Rochester, England, said the Vatican's announcement showed a "generosity of spirit."

But he questioned whether the new system would uphold Anglican traditions in the training of new priests. "Before some fundamental issues are clarified, it is difficult to respond further to what the Vatican is offering."

---Margherita Stancati contributed to this article