WASHINGTON - Federal health officials are recommending an end to the nation's lifetime ban on blood donations from gay and bisexual men, a 31-year-old policy that many medical groups and gay activists say is no longer justified.

The Food and Drug Administration said Tuesday it favors replacing the blanket ban with a new policy barring donations from men who have had man-on-man sex in the previous 12 months. The new policy would put the United States in line with other countries including Australia, Japan and the U.K.

Activists, however, questioned whether requiring a year of celibacy from gay men in order to donate blood amounted to a significant policy shift.

The lifetime ban dates from the early years of the AIDS crisis and was intended to protect the blood supply from what was a then little-understood disease. But many medical groups, including the American Medical Association, say the policy is no longer supported by science, given advances in HIV testing. Gay activists say the ban is discriminatory and perpetuates negative stereotypes.

The agency will recommend the switch in draft guidelines early next year and move to finalize them after taking comments from the public, FDA officials told reporters. FDA Deputy Director Peter Marks declined to give a time frame for completing the process but said, "we commit to working as quickly as possible on this issue."

Marks said some of the most compelling evidence for changing the policy comes from Australia, which put in place a one-year ban on donations over a decade ago. Recently published studies showed no change in the safety of the blood supply after making the switch.

Additionally, studies conducted by the U.S. government suggest gay and bisexual men are actually more likely to abide by donation guidelines under a 12-month prohibition period. All blood donors take a questionnaire about their health and sexual behavior, but some gay men reportedly answer inaccurately to donate blood.

All U.S. blood donations are screened for HIV, but testing only detects the virus after it's been in the bloodstream about 10 days. Still, FDA officials said current research does not support reducing the donation ban below the one-year mark, though the agency may consider changing the time frame in the future.

"We're committed to reevaluating the blood donor deferral policy in the future as new scientific evidence becomes available, but at this time we simply don't have the evidence," Marks said.

According to government figures, men who have had sex with other men represent about 2 percent of the U.S. population, yet account for at least 62 percent of all new HIV infections in the U.S.

The American Red Cross estimates the risk of getting an HIV-positive blood donation is 1 in 1.5 million. About 15.7 million blood donations are collected in the U.S. each year.

Despite the shift from federal officials, gay advocates said Tuesday that requiring a year of abstinence from gay and bisexual men was unrealistic and not supported by science.

"This new policy cannot be justified in light of current scientific research and updated blood screening technology," said David Stacy of Human Rights Campaign, the largest U.S. gay rights group.