WASHINGTON, July 22 (Reuters) - The U.S. Centers for Disease Control and Prevention said on Tuesday it will soon release long-awaited revised estimates of how many Americans become infected with the AIDS virus every year.

Activists have been saying the numbers are sharply higher and have been urging the CDC to release the numbers.

In June, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said he believed the numbers had risen from 40,000 to 50,000 a year, although the CDC denied he had seen the new estimates.

Late on Tuesday, the CDC said it would release the new estimates on Aug. 3 in the Journal of the American Medical Association.

"These new incidence estimates are based on direct measurement of new HIV infections and will provide the clearest picture to date of incidence (or the number of new HIV infections in a given year)," it said in a "Dear Colleague" letter.

"These more precise estimates are possible now only because of breakthrough technology developed by CDC that can distinguish recent from long-standing HIV infections."

Because the system was new, it had to "receive rigorous scientific review," the CDC said.

"This process took longer than we anticipated, but, in the end, it has produced estimates that are more reliable and scientifically sound than would have occurred without the independent review."

In June, Fauci said the new counting methods were not changing the overall picture of AIDS in America, but reflected the long-standing rate of new infections.

In the United States, with a population of about 300 million, 1.1 million people are infected with HIV, of which 25 percent do not know it.

Globally, an estimated 33.2 million people are infected with the human immunodeficiency virus that causes AIDS and 25 million have died so far. It is mainly transmitted through heterosexual sex but also mother to child and via needles.

Knowing the precise number of new infections is key to better funding for clinics, public education and drug programs. HIV has no cure and there is no vaccine, but treatment with drugs can keep the infection under control and people who know they are infected can take steps to avoid infecting others.

(Reporting by Maggie Fox; Editing by Eric Beech)

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