Laughing after the meeting, Rogge, who is also a medical doctor, said they had had major difficulties explaining the technical issues involved to the board members with non-medical backgrounds. 'Even for me this is very complicated,' he said, adding they would rework the proposal in layman's terms and present it to the board again at the next meeting in Switzerland in May.

The IOC described it as a 'very sensitive and controversial issue', but also said the board supported the proposal in principle and it was now just a matter of 'clearly defining the exact medical criteria that will be used to decide who can compete'.

The issue has landed on China's lap as - with the Athens Games fast approaching - the IOC said it was most likely Beijing would have the distinction of being the first Summer Games in which transsexuals were permitted to compete.

Down through the decades, several athletes born as men have sought to compete in women's sporting events. Others have been born sexually ambiguous, hermaphrodites with both male and female sexual organs or chromosomes, while still others have found their bodies transforming after sustained use of potent steroids.

Naturalised American Stella Walsh, competing under her Polish name Stanislawa Walasiewiczowna, won 100 metres gold in the 1932 Olympics and silver in the 1936 Games. She set 11 world records in her career, but when an autopsy was performed after she was shot dead in a robbery in 1980 it turned out she had both male and female chromosomes, with a tiny penis and testes and no female organs. Under current IOC rules she was technically a man, but they are now wondering if that should also change.

Also in the 1936 Berlin Games, German Hermann Ratien came fourth in the women's high jump competition, but decades later admitted he had pretended to be a woman.

Tamara Press, a thrower, and her sister Irina, a hurdler, won five gold medals for the Soviet Union, but when gender verification tests were introduced after the 1964 Olympics, the pair disappeared and never competed again. There was widespread speculation at the time that they had actually been men.

At the 1968 Olympics Polish sprinter Ewa Klobukowska became the first athlete to fail the gender test, with medics saying she 'had one male chromosome too many', while East German Heidi Krieger was pumped full of so many anabolic steroids to become 1986 European shot putt champion that her body became sexually disturbed. In 1997 she had a sex-change operation and now lives as Andreas Krieger with his wife, Ute.

And in 1977 the tennis world was rocked when Renee Richards, known as Richard Raskind before her sex-change operation, won a court judgment to be allowed to compete in the women's US Open. The following year, aged 44, she reached the quarter finals of the same tournament, later going on to become Martina Navratilova's coach.

More recently, cycling has also confronted the issue by allowing Michael Dumaresq, who had a sex-change operation in 1996, to compete for Canada in the 2002 women's world mountain bike championships as Michelle Dumaresq. Her participation prompted widespread protests and more than 300 of her female competitors signed a petition protesting against the liberalised ruling.

Controversy was also courted on the golf circuit earlier this month when transsexual Mianne Bagger created history by becoming the first male-born female to play at a national golf championship, after she was granted a sponsor's invitation to compete in the women's Australian Open in Sydney.

Some argue men who have become women have a physical advantage over athletes who were born women as men have higher levels of testosterone, a larger heart and lung capacity and a greater muscle-to-fat ratio.

Bagger denied that she had a strength advantage over the other golfers, pointing out that she hits her drives about 210 yards, shorter than most of the field.

'People don't understand transsexualism,' she said at a press conference after she failed to make the cut in the competition. 'When you undergo sex-change surgery, physiological changes include losing muscle mass and strength. After surgery there's nothing left in our bodies that produces testosterone. Now I have less testosterone than the average levels for women in society.'

Schamasch, who is the IOC medical director, agrees with her, saying that specialists in the field found that testosterone levels and muscle mass drop after sex-change surgery and hormone therapy.

Dumaresq, the cyclist and a full-time metal worker, said that after her hormone treatment and sex-change operation her body was greatly weakened. 'I needed regular gym workouts just to build up enough strength to continue my job,' she said, adding that her larger-boned legs were more of a hindrance than a help on the biking circuit. 'It actually made things harder because after the hormone treatment and operation I no longer had the muscle mass to support my bones. This so-called advantage I'm supposed to have doesn't exist.'

Schamasch said that while the proposal details were still being ironed out, he believed transsexual athletes should be eligible for the Olympic Games once a set amount of time had elapsed after their sex-change surgery, adding that an athlete could compete in his or her new sex once doctors had verified that certain medical conditions had been fulfilled.

A source close to the Olympic organising committee in Beijing said news of the proposal had bemused many local officials but they realised they ultimately had to toe the IOC's line.

As the city ploughs ahead with massive infrastructure projects in preparation for 2008, there is a growing sense of belief locally that Beijing will host an impressive Olympics. 'Enormous efforts are being made to make the Beijing Games memorable,' the source said. 'but it's funny to think they might be unforgettable for the sight of women, who were once men, winning Olympic gold.'