LONDON (AP) -- The most powerful force against AIDS in Africa may be circumcision, a procedure that's easily done in the developed world. But it's a challenge on a continent where there are too few medical workers and a reluctance by men for cultural reasons and fear of pain.

Now there may be a new weapon in the arsenal -- a ring-shaped device that is mostly painless and requires less time for health workers.

The Chinese-developed device, the ShangRing, has been tested in a small study in Kenya and a larger test is set for later this year. The Bill & Melinda Gates Foundation will invest about $4 million into studying the device.

The drawback is that men must wear the ShangRing for 10 days, but at least one man who tried it found it surprisingly painless.

Christopher, a Kenyan farmer who asked that only his first name be used, decided to get the ring after hearing how painful traditional circumcision was.

"I thought it would be the best way to protect against diseases (like) AIDS," he said, adding there was little pain when the ring was put on. He said more Kenyan men should be able to try the ring, and didn't find it difficult to wear the ring for so long.

Scientists think circumcision reduces the chances of HIV infection because the foreskin is particularly susceptible to HIV.

The ShangRing consists of two plastic rings, one slightly smaller than the other, that trap the foreskin in between them. With the use of some anesthesia, the foreskin can then be snipped off without major bleeding or stitches. The device is kept on for 10 days to allow the wound to heal.

According to Chinese data, the complication rate in thousands of men who have had the ShangRing is less than 5 percent. In traditional circumcisions in Africa, it can be as high as 15 percent. A surgical circumcision takes about 20 minutes; one with the ShangRing can be done in about five.

"The ShangRing could have a huge impact on reducing HIV transmission," said Marc Goldstein, a professor of reproductive medicine and urology at New York Presbyterian Hospital and Weill Cornell Medical Center. Goldstein, who does not have any financial ties to the ring, and colleagues conducted the Kenya testing.

In the 40 men tested in Kenya, 90 percent said they were satisfied with the procedure.

In recent years, health officials have been scrambling to figure out how to circumcise about 50 million men across Africa - where 70 percent of the world's HIV-infected population lives. "Circumcision is unlike a vaccine," said Dr. Renee Ridzon, an AIDS expert at the Gates Foundation. "It has certain challenges."

Countries with high HIV rates, including Botswana, Kenya, Rwanda, Namibia and Zambia, have all added circumcision to their prevention campaigns.

While circumcision tools have long been used for babies, few have been developed for adults. The Gates Foundation had biomedical engineers examine the available handful of adult circumcision devices, including a clamp Ridzon described as "cage-like."

In some parts of Africa, cultural issues are a sticking point. Some tribes in South Africa perform circumcision as a rite of passage, but others do not consider circumcised men to be "complete."

Experts are also concerned men who get circumcised will mistakenly think they are immune to HIV. That was the case for Samson Agalo, a bicycle taxi operator from Kisumu, Kenya, who recently had a circumcision - and has been having sex with multiple partners ever since. "After going for the cut, you don't need condoms," he said.

Kim Dickson, an AIDS expert at the World Health Organization, said mass circumcision could prevent about 4 million adult HIV infections between 2009 and 2025.

"Circumcision will likely avert far more deaths per dollar spent than other things we're spending HIV money on," said Philip Stevens, of the London-based think tank International Policy Network. "The main problem I can foresee with this is actually persuading men to sign up for it."

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