A leading US doctors' group this week urged the reversal of a decades-old ban on donations of blood from gay men, saying the law is discriminatory and outdated.

The policy decision came Tuesday in Chicago at the annual meeting of the American Medical Association, a professional grouping of more than 800,000 doctors.

"The lifetime ban on blood donation for men who have sex with men is discriminatory and not based on sound science," said AMA Board member William Kobler.

"This new policy urges a federal policy change to ensure blood donation bans or deferrals are applied to donors according to their individual level of risk and are not based on sexual orientation alone."

The US ban was implemented in 1983 in response to the AIDS outbreak, and prohibits blood donation from any man who has had sex with another man at any point since 1977.

"It is long past time we reformed our blood donation policy affecting gay men," said Chris Collins, director of public policy at The Foundation for AIDS Research, branding the ban a "a non-evidence-based, stigmatizing law."

The call for a change to the Food and Drug Administration's policy is a stance shared by the American Red Cross, America's Blood Centers and the AABB, an international association of professionals in transfusion medicine.

Those groups in 2010 urged the FDA to change its lifetime ban to a 12-month deferral for blood donation, like that which exists for other high-risk groups, meaning men should wait 12 months to donate blood after having sex with another man.

Current US standards require a 12-month waiting period before blood donations from people who have had sex with someone with HIV or viral hepatitis.

Screening tests usually detect HIV within nine days and hepatitis C in about seven days, the Red Cross said.

The Health and Human Service's Advisory Committee on Blood Safety and Availability held a meeting on the matter in 2010. Concerns were expressed about the need for more research on preventing risks to the blood supply.

The FDA says on its web site it is still examining research and will consider a policy change if new approaches to donor screening and testing "can assure that blood recipients are not placed at an increased risk of HIV or other transfusion transmitted diseases."