After 12 years of debate and hesitancy, the U.S. government's three leading public-health agencies will issue a joint statement today declaring that latex condoms, when properly used, are highly effective in blocking the spread of the AIDS virus.

"There's been a lot of debate about the product, condoms," said Dr. Bert Peterson, a researcher in the Centers for Disease Control and Prevention's Division of Reproductive Health. "What these studies show is that the problem is not with the product. The problem is with the user.

"We think everyone needs to have this information, including teenagers," Peterson said. "It's analogous to having a vaccine. So our message to school-age youth is: Avoid intercourse with an infected individual or an individual at risk. If you are having intercourse, use a condom, and use it consistently and properly."

Friday's statement, to be issued by the CDC, National Institutes of Health and the Food and Drug Administration, was said to represent the strongest federal government support for condom use.

At the same time, a new CDC survey indicated that Americans have little confidence in condoms. In 1987, Peterson said, a third of surveyed adults said they thought condoms worked both as birth control and disease prevention. By 1991 only 28 percent expressed confidence in condom reliability. Furthermore, most Americans still don't know how to use a condom properly - 75 percent were unaware that latex condoms dissolve and leak when used with petroleum-based lubricants.

The government report, to appear in today's Morbidity and Mortality Weekly Report, says "latex condoms are highly effective for preventing HIV (human immunodeficiency virus) infection and other STDs (sexually transmitted diseases) when used consistently and correctly. Condom availability is essential in assuring consistent use. Men and women relying on condoms for prevention of HIV infection or other STDs should carry condoms or have them readily available."