A pill that has long been used to treat HIV has moved one step closer to becoming the first drug approved to prevent healthy people from becoming infected with the virus that causes AIDS.

The Food and Drug Administration said Tuesday that Gilead Sciences' Truvada appears to be safe and effective for HIV prevention. It concluded that taking the pill daily could spare patients "infection with a serious and life-threatening illness that requires lifelong treatment."

On Thursday a panel of FDA advisers will consider the review when it votes on whether Truvada should be approved as a preventative treatment for people who are at high risk of contracting HIV through sexual intercourse. The FDA is not required to follow the advice of its panels, but it usually does.

An estimated 1.2 million Americans have HIV, which attacks the immune system and, unless treated with antiviral drugs, develops into AIDS, a fatal condition in which the body cannot fight off infections. If Truvada is approved, it would be a major breakthrough in the 30-year campaign against the AIDS epidemic. There have been no other drugs proven to prevent HIV and a vaccine is believed to be decades away.

--ASSOCIATED PRESS