The decision by the US Food and Drug Administration brings US policy in line with several other developed nations, including France, Japan and Australia, which all recently moved to allow men who have sex with men (MSM) to donate blood, as long as they have not had intimate relations in the past year.
The new rule overturns a ban that dates to 1983, when the AIDS epidemic was just emerging and many experts were fearful of contaminating the blood supply with a poorly understood disease.
"Ultimately, the 12-month deferral window is supported by the best available scientific evidence, at this point in time, relevant to the US population."
The ban remains in place for commercial sex workers and people who use injection drugs, because "insufficient data are available to support a change to the existing deferral recommendations at this time," the FDA said in a statement.
"These published studies document no change in risk to the blood supply with use of the 12-month deferral," it said.
People with hemophilia or related clotting disorders are also still barred from donating blood "for their own protection due to potential harm from large needles used during the donation process," the FDA said.