The announcement by Pope Benedict XVI today that he will resign over health issues – the first time a pope has resigned in hundreds of years, left American religious leaders stumbling for words.

“We are, of course, all surprised today by the announcement of the pope that he will resign at the end of the month,” said Father Frank Pavone, national director of Priests for Life.

“Popes have the authority to do this, of course, though it has rarely been exercised.”

While speculation immediately was launched regarding a possible replacement, Pavone focused on what Benedict had done.

“We view the pope’s action here in a positive light, as an expression of his concern and love for the church. He wants the church to have a pope who can fulfill his role with the strength and vigor that the office requires,” said Pavone, whose organization is the largest Catholic pro-life group dedicated to ending abortion and euthanasia.

“My own interactions with Pope Benedict have been in the arena of his defense of human life, and we at Priests for Life thank him in particular for the ways in which he has continued to announce and implement the church’s pro-life teachings,” he said.

Officials with the Catholic League simply said the pope’s legacy is secure.

Bill Donohue said it was Benedict who “made it clear that religious freedom was not only a God-given right, it was ‘the path to peace.’”

In a posted statement, the organization said Benedict’s “many references to what he called ‘the dictatorship of relativism’ were a constant reminder that one of the greatest threats to freedom today is the abandonment of the search for truth.”

The Catholic League noted the pope’s work on reaching out to non-members and his crackdown on priestly sexual abuse.

The pope’s “willingness to step aside comes as a surprise this Monday morning. What is not surprising is his humility,” the statement said. “Indeed, it is one of his most defining characteristics, one that separates him from today’s egocentric public figures.”

His resignation letter said,” After having repeatedly examined my conscience before God, I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry.”

Officials said it is the first time in almost 600 years that a pope to resign.

The author of “From Sabbath to Sunday” spent years at the Pontifical Gregorian University in Rome, and explains the “political, social, pagan and Christian” factors that changed “a Holy Day into a holiday.”

New York Cardinal Timothy Dolan told CBS he was as startled as the rest of the world.

In a statement, Dolan said, “He unified Catholics and reached out to schismatic groups in hopes of drawing them back to the church. More unites us than divides us, he said by word and deed.”