South Korea's Olympic swimming champion Park Tae-hwan choked back the tears on Friday as he apologized for a failed doping test that led to an 18-month ban from the sport and said he wished he could turn back time and do things differently.

Swimming's governing body FINA handed out the ban on Monday at a hearing in Switzerland after the 25-year-old had tested positive for testosterone ahead of the Asian Games in September.

Park, one of South Korea's most popular athletes and the face of a host of advertising campaigns, tested positive after he was given a shot at a clinic and said he should have taken more care to find out what the doctor was injecting him with.

"The last few months since the doping results came out have been hell," Park told reporters at a Seoul hotel. "When I first heard that I had tested positive I thought for sure it must be some mistake.

"I thought, 'Why did this happen to me? What if I didn't go to that hospital? What if I didn't let the doctor inject me? If I could only go back in time."

Park said he had gone to the clinic seeking treatment for a skin complaint and after being prescribed vitamins he had explained to the doctor that he could not take anything that might be on the banned substances list.

The hospital had assured him he was only receiving vitamins, he added.

South Korea's Yonhap news agency has reported that Seoul prosecutors have charged a doctor with professional negligence and the trial is set to begin next month.

A double world champion and the first Korean to win an Olympic swimming medal, Park's suspension was backdated from September 3 and runs through March 2, 2016, leaving the door open for Park to return in time for the Rio Olympic Games.

Park's case has stunned the sporting community in South Korea, which took enormous pride from his 400 meters freestyle gold medal at the 2008 Beijing Olympic Games.