WASHINGTON (Reuters):

Giving women diaphragms to use in addition to condoms provides no extra protection against the AIDS virus, researchers reported on Thursday.

The hope was that a female-controlled method of contraception might give women a little extra protection against the virus, especially when so many men are reluctant to use condoms.

But the approach failed to help, Dr. Nancy Padian of the University of California San Francisco and colleagues found.

"These results do not support the addition of the diaphragm to current HIV prevention strategies. Condoms remain the only proven barrier method for HIV prevention," Padian said in a statement.

"Women who cannot convince their male partners to use condoms are still in urgent need of a female-controlled method of protection," the researchers wrote in their report, published in the Lancet medical journal.

"In addition to research on methods that are inherently more efficacious, we must develop the instruments to allow assessment of even modest amounts of protection."

They tested 5,045 women in South Africa and Zimbabwe, giving them all an HIV-prevention package, consisting of condoms, pre-test and post-test counselling about HIV and sexually transmitted infections, testing and treatment. Half the women also got diaphragms.

But the incidence of the human immunodeficiency virus that causes AIDS was the same in both groups - around four per cent.

"We observed no added protective benefit against HIV infection when the diaphragm and lubricant gel were used in addition to condoms and a comprehensive HIV prevention package," the researchers wrote.

AIDS, which infects close to 40 million people globally, is now transmitted mostly during sex between a man and a woman. There is no cure and the virus has killed 25 million people.