Benedict said in an interview that for some people, such as male prostitutes, using condoms could be assuming moral responsibility because the intent was to reduce infection. The pope did not suggest using condoms as birth control, which is banned by the church, or mention the use of condoms by female prostitutes.
Theologians have long been studying the possibility of condoning such limited condom use as a lesser evil. There were reports years ago that the Vatican was considering a document on the subject, but opposition to any change has apparently blocked publication.
One Vatican official said Monday he believes the pope just "decided to do it" and get a debate going.
For the deeply conservative Benedict, it seemed like a bold leap into modernity - and the worst nightmare of many at the Vatican. The pope's comments set off a firestorm among Catholics, politicians and health workers that is certain to reverberate for a long time despite frantic damage control at the Vatican.
In a sign of the tensions within the Vatican, the Holy See's chief spokesman, the Rev. Federico Lombardi, rushed out a statement to counter any impression that the church might lift its ban on artificial birth control. Lombardi stressed that the pope's comment neither "reforms or changes" church teaching.
"The reasoning of the pope cannot certainly be defined as a revolutionary turn," he said.
While much of the world hailed Benedict's statement, seeing it as a major step toward lifting the church ban, conservatives were mortified and insist the pontiff was not "justifying" condom use from a theological point of view.
True, Benedict made only a tiny opening, but he stepped where no pope has gone since Pope John Paul II's 1968 encyclical "Humane Vitae" that was supposed to have closed debate on church policy barring Catholics from using condoms and other artificial means of contraception.
The pope chose to make his statement not in an official document but in an interview with a German journalist, Peter Seewald, for the book "Light of the World: The Pope, the Church and the Signs of the Times." L'Osservatore Romano, the Vatican newspaper, first published excerpts of Benedict's comments on Saturday.
Luigi Accattoli, a veteran Vatican journalist who will be on the Vatican's panel when the book is presented Tuesday, said Benedict had taken a "long awaited" step that only the highest authority of the church could do.
In March 2009 Pope Benedict was criticized for a statement he made while traveling to Cameroon, where UNAIDS states 540,000 people were living with HIV/AIDS in 2007, 39,000 had died, and 300,000 children were orphaned by the disease.
In discussing with reporters the AIDS crisis, Benedict said, "You can't resolve it with the distribution of condoms."
Since the pontiff's latest remarks were disseminated, health officials have expressed optimism.
This weekend UNAIDS Executive Director Michel Sidibe said, "This is a significant and positive step forward taken by the Vatican today.
"This move recognizes that responsible sexual behavior and the use of condoms have important roles in HIV prevention."
Speaking in Berlin on Monday, the director-general of the World Health organization, Margaret Chan, welcomed the pope's position. "For the first time the use of condoms in special circumstances was endorsed by the Vatican, and this is good news and good beginning for us."
Jon O'Brien, president of the Washington-based Catholics for Choice, called the pope's comments "a marvelous victory for common sense and reason and a major step forward towards recognizing that condom use can play a vital role in reducing the future impact of the HIV pandemic."
Some Catholic believers expressed praise and wariness for the pope's comments, and greeted them as a sign that the church was stepping into the modern debate in the fight against AIDS.
Others cautioned it could open a doctrinal Pandora's box.
Ellen Reik, a 79-year-old retired housewife who attended Mass at Saint Michael Catholic Church in Worthington, Ohio, said if taken out of context, the pope's remarks could renew the debate over the morality of birth control - both as a contraceptive and a means to curb the spread of sexually transmitted diseases.
As she left Mass at St. Kieran Church in the Coconut Grove neighborhood of Miami, Lois Breaux rolled her eyes when asked about the Pope's statements.
"About time - and it wasn't enough," she said. "As a Catholic, they need to recognize this is an epidemic. The church needs to stand up and say what he did, but he should have gone further."
Jean Jasman, an 81-year-old state worker from Montpelier, Vt., called the stance a departure from church doctrine on condom use, "but it's to the betterment of humanity, if we can help prevent the spread of this horrendous disease."
Speaking shortly before Mass began at St. Mary of the Lake Roman Catholic Church in Lakewood, N.J., 42-year-old Jason Randall said he strongly supports the church's position that forbids the use of condoms and other contraceptives.
But he felt the pope's comments show that sometimes exceptions are needed for almost every rule.
"I know it's a cliche to put it this way, but if it helps prevent even one death or one person getting sick, it's worth it," Randall said. "I believe in a loving God, one who does not want people to suffer, whether they be saints or sinners."
"I think that the church needs to realize that sometimes you have to make adjustments with the times, and that saving people's lives and protecting life is ultimately the most important thing," said Josephine Zohny of Brooklyn, N.Y., after leaving Mass at St. Patrick's Cathedral in New York.
For more info:
"Light Of The World: The Pope, the Church and the Signs of the Times" by Pope Benedict XVI, Peter Seewald (Ignatius Press)