TORONTO -- Canada is lifting a nearly 30-year-old ban on gay men giving blood, though for the time being only those who are abstinent will be allowed to donate.

The new policy, which Canadian Blood Services hopes to have in place by mid-summer, will allow men to donate blood if they haven't had sex with another man for five years before the donation.

The agency understands that the length of this deferral won't satisfy all critics. But agency executive Dana Devine said this is the first step in what Canadian Blood Services hopes will be a continued effort to work out what is the best approach to incorporating gay men into the donation community.

"So the message to them today is to simply bear with us," Devine, vice-president of medical, scientific and research affairs at Canadian Blood Services, said in an interview.

"We are working toward attempting to make the opportunity for additional people to donate blood ... and we just aren't quite there yet for that group of people."

The policy change has been in the works for several years and has involved consultation with groups representing would-be donors as well as hemophiliacs who rely on blood transfusions and those who could be harmed if screening systems aren't adequate to keep pathogens out of the blood supply.

Health Canada gave approval to Canadian Blood Services and its Quebec equivalent, Hema-Quebec, on Wednesday.

The lifetime ban against donations by gay men was instituted in the mid 1980s by the Red Cross, which was then responsible for the blood supply system. The move was taken when it was realized that the alarming new disease AIDS, which was then untreatable, could be contracted through blood transfusions.

In fact, hundreds of Canadians were infected with HIV and-or hepatitis C in the era before tests to screen out contaminated blood were developed and adopted by the Red Cross. A Royal Commission, the Krever Inquiry, later determined the Red Cross had not moved quickly enough and recommended stripping it of authority for the blood system. It also called for compensation for people injured by tainted blood.

That history cast a long shadow over the work to lift the lifetime ban and explains the current go-slow approach.

Dr. Mark Wainberg, a McGill University HIV researcher and a former president of the International AIDS Society, welcomed the move.

"I think it is a step in the right direction regarding non-discrimination and stigmatization of gay men," Wainberg said via an email.

Devine said this step will help the blood agencies gather safety data that may later be used to open up blood donation to more gay men. Critics of the policy have argued that gay men who are in long-term monogamous relationships should be allowed to give blood if they wish.

The change announced Wednesday will open the door to men who may have had an experimental sexual encounter with another male when they were young, as well as men who were raped when they were boys, Devine said. The lifetime ban applied to any man who had had a sexual encounter with another man, encompassing as a result some men who did not live as gay men, she noted.

A number of other countries already allow gay men to give blood, and some use a shorter deferral period than Canada has settled on.

In Britain and Australia, gay men who haven't had sex with other men for at least a year are eligible to donate. In South Africa the deferral period is six months. But the United States still retains a lifetime ban.