Catholic reformers and groups working to combat HIV have welcomed remarks by Pope Benedict that the use of condoms might not always be wrong.
The Pope said their use might be justified on a case by case basis to prevent the spread of HIV/Aids.
The remarks, due to be published in a book next week, mark a softening of his previously hard line against condoms in the battle against HIV, analysts say.
The Vatican has long opposed condoms as an artificial form of contraception.
This has drawn heavy criticism, particularly from Aids campaigners, who say condoms are one of the few methods proven to stop the spread of HIV.
'Significant shift'Pope Benedict said during a visit to Cameroon last year that handing out condoms might actually make HIV infection worse, drawing criticism from several EU states.
In his latest comments, however, he said the use of condoms might be justified in exceptional circumstances.
He gave the example of male prostitutes where, he said, using condoms to prevent the spread of AIDS could be seen as an act of moral responsibility, even though condoms were "not really the way to deal with the evil of HIV infection".
This marks a significant shift in his previously implacable opposition to the use of condoms, says the BBC's religious affairs correspondent, Robert Pigott.
UNAIDS, the United Nations programme on HIV/Aids, welcomed the comments as a "significant and positive step forward".
"This move recognises that responsible sexual behaviour and the use of condoms have important roles in HIV prevention," said UNAIDS Executive Director Michel Sidibe.
The Kenya Treatment Access Movement (KETAM), which works to combat the spread of HIV, welcomed what it said was the Pope's acceptance of reality that abstinence did not always work.
"It's accepting the reality on the ground," said David Kamau, head of the KETAM. "If the Church has failed to get people to follow its moral values and practice abstinence, they should take the next best step and encourage condom use".
The Catholic reform group We Are Church said the comments showed the Pope was able to learn from experience.
The British gay rights campaigner, Peter Tatchell, told the BBC the Pope's comments were significant but needed "clarification".
BBC News
