The U.S. Food and Drug Administration says it's proposing to allow blood donations by gay and bisexual men, but with the requirement that they've abstained from gay sex for at least a year.
That would bring to a close the lifetime ban on such donations instituted in 1983 in the first years of the AIDS crisis.
Medical experts have long urged such a change, noting advances in HIV testing of blood supplies have made the rigorous ban unnecessary.
Gay rights groups have criticized that lifetime ban on blood donations, saying it promotes the perpetuation of stereotypes.
The new proposal on gay and bisexual men as blood donors would be in line with that applied to other men and women at increased risk for HIV infection, the FDA said.
After issuance of a draft proposal, expected early next year, and a period of public comment, a final guidance would be issued "as quickly as possible," said Peter Marks, deputy director of the FDA's Center for Biologics Evaluation and Research.
The FDA said the proposal was formulated after it "carefully examined and considered the available scientific evidence," taking into account a number of recent studies.
The new policy would match initiatives already in place in Britain, Japan and Australia.
It would also be in line with other legal and political rights granted to gays, such as the right to marry and to serve in the military openly.
"This is a major victory for gay civil rights," says I. Glenn Cohen, a law professor at Harvard University who specializes in bioethics and health. "We're leaving behind the old view that every gay man is a potential infection source."
However, some gay groups disagreed and criticized the proposed policy, calling any ban at all offensive and unnecessary.
"By implementing this policy, the FDA will continue to fan the flames of the outdated stereotype that HIV is only a 'gay disease,'" the organization Gay Men's Health Crisis said.
The policy contains no requirement of a year-long celibacy for straight blood donors, the group pointed out.
Since 1977, on the FDA questionnaire for prospective blood donors, men have been asked if they've indulged in gay sex.
The 1-year deferral the FDA is proposing was also recommended last month by the U.S. Department of Health and Human Services.
When asked about the possibility of a ban shorter than one year, Marks said scientific evidence supporting such an option was not "compelling."
Experts say the new policy could increase the annual supply of donated blood.
The change could bring more than 300,000 additional pints of blood to the country's supply annually, said the Williams Institute at UCLA.
