PARIS (Reuters) – Pope Benedict's surprising view that condoms can sometimes be used to fight AIDS has kindled a lively debate among Roman Catholic theologians and commentators about whether this amounts to a change in Church thinking.

His comments and a Vatican clarification that expanded on them seem to leave no doubt that Benedict has spoken with unprecedented frankness for a pontiff and shifted the focus a bit from the Church's rejection of condoms to avoid disease.

But the format of his remarks — in a book of interviews with a German journalist rather than an official Vatican document — and some confusion over translations have opened a gap allowing divergent interpretations.

Conservative Catholic bloggers have reacted with dismay — one put the book title 'Light of the World' over a cartoon of Pandora opening her box and letting the world's evils escape.

"I love the Holy Father very much, he is a deeply holy man and has done a great deal for the Church. On this particular issue, I disagree with him," wrote Rev. Tim Finigan on his blog The Hermeutic of Continuity.

The pope's US publisher, Rev. Joseph Fessio, declared: "The pope did not 'justify' condom use in any circumstances. And Church teaching remains the same as it has always been — both before and after the pope's statement."

Those who have long argued for allowing condoms as a last resort welcomed the new approach.

"The Vatican has been so critical of condoms that it has led some Catholics to think that condoms are somehow intrinsically evil, that there is no conceivable situation where they could be used morally," Rev. Thomas Reese said in Washington.

"The pope's new statement blasts that idea out of the water," said the senior fellow at Woodstock Theological Centre.

Christian Terras, normally a sharp critic of Benedict in his dissident French Catholic magazine Golias, called the tone of the pope's approach "more human and pastoral, closer to the people, less professorial and cerebral".

The Vatican has never issued an official doctrine on condom use and AIDS. Its rejection of condoms stems from the encyclical Humanae Vitae that banned all forms of artifical birth control in 1968 and its teaching that sex must be reserved for married couples.

This stand increasingly came under fire when AIDS swept Africa and health workers advised condom use to avoid spreading the virus HIV. Critics decried Popes John Paul and Benedict as murderers for advocating abstinence and marital fidelity alone.

Moral theologians have argued for years that condom use to avoid transmitting the deadly virus could be condoned as a last resort under the commandment "Thou shalt not kill".

In the book, Benedict said condoms could be used as a last resort and as a first step towards a more moral approach to sexuality. By first limiting this to male prostitutes, he also set off discussion about the conditions he was setting for this.

After the Vatican daily L'Osservatore Romano wrote that this was limited to female prostitutes, spokesman Rev. Federico Lombardi said earlier this week the pope had assured him his approach applied even more widely that the book implied.

"If it is a man, a woman or a transsexual who does it, we are always at the same point, which is the first step in responsibly avoiding passing on a grave risk to the other," he told a news conference to present the book at the Vatican.

"The fact that an official Vatican spokesperson seems to be extending the possibility of use clearly is groundbreaking," said Rev. John Pawlikowski, a professor of social ethics at the Catholic Theological Union in Chicago.

French Cardinal Philippe Barbarin said the pope had not changed Church doctrine but he had "highlighted nuances, because human situations are sometimes very complex".Barbarin, the doctrinally conservative archbishop of Lyon, said the pope simply reaffimred what the late Paris Cardinal Jean-Marie Lustiger had said 20 years ago: "If you don't want to be saints, at least don't become murderers."