Australia's Olympic swimming champion Zac Stubblety-Cook says the anti-doping system has failed and is weighing a possible protest after racing a drug-tainted Chinaman.
Stubblety-Cook will defend his Olympic 200m breaststroke at the Paris Games against a field including China's world record holder Qin Haiyang.
Qin is among 23 Chinese swimmers who tested positive before the Tokyo Olympics but was still allowed to compete at the Games three years ago.
World ant-doping authorities accepted China's explanations that the positive tests stemmed from swimmers eating contanimated food at a team hotel.
Stubblety-Cook remains disappointed at revelations of the positive China drugs tests.
"I absolutely believe in clean sport and I hope that this is a clean Games," Stubblety-Cook told reporters on Thursday.
"It's obviously disappointing to hear that news and hear about the pre-Tokyo 23 athletes testing positive, some multiple times.
"And for me, racing someone that was one of those athletes and finding out he was one of those athletes was disappointing.
"It's less about what country they came from and more about the system and how the system ultimately feels like it's failed. And that's the truth."
Qin defeated Stubblety-Cook for the 200m breaststroke title at last year's world championships in Japan when the Chinese swimmer set a world record.
Now-retired Australian swimmer Mack Horton famously refused to stand on the podium at the 2019 world championships alongside China's Sun Yang, who had previously been banned for drug use.
Stubblety-Cook stopped short of committing to reprise Horton's protest at the Paris Olympics.
The International Olympic Committee's rule 50 permits athletes some freedom to express opinions on political or social issues but protests on medal podiums or the field of play are banned.
"Everyone probably is aware of rule 50 here and the repercussions that happen with that," Stubblety-Cook said.
"I think potentially we could see protests in other events as well.
"Personally, I think I will make a decision probably on the day.
"At the end of the day, I'm a clean athlete and I'm trying to abide by those rules and I just hope my competitors do the same."
Stubblety-Cook's comments came as the World Anti Doping Agency president Witold Banka said doping could never be eradicated.
"It's obvious that you will never eliminate doping from the sporting landscape," Banka told reporters on Thursday.
"You will always find someone who wants to cheat."
