(Reuters) - South Africa's big Olympic swimming hope Chad Le Clos has revealed that both his parents are battling cancer as he prepares for next month's Rio Games.

The 200 meters butterfly champion, whose father Bert became a media sensation at the London 2012 Games for his exuberant reaction to his son's gold, said he hoped they would be accompanying him to Brazil.

"My mum Geraldine has breast cancer which has returned since her remission in 2010," Le Clos, who beat American Michael Phelps to gold four years ago, said in a statement.

"She has recently undergone a double mastectomy and is now having chemo. My dad Bert developed prostate cancer and has also undergone an operation in late June.

"It has not been an easy time but I am training hard for Rio. More than anything else I want them to win their battles," said the 24-year-old, who is also the 100m butterfly world champion and Olympic silver medalist.

The showdown in the pool with 18-times Olympic champion Phelps is set to be a highlight of the Rio meet.

Le Clos has booked a spot in five different events after securing required qualifying times at the South African swimming championship in April, but whether he will feature in all of them is unclear.

He said last year that he planned to take on Phelps in the 100m and 200m butterfly and freestyle races at the Aug. 5-21 Games but has since scrapped the 100m freestyle.

"Thinking about what has happened to both my parents has helped a lot with my motivation," he told the BBC.

"There are many pressures on me, but I know when I step on the starting block in an Olympic final that I can handle anything that gets thrown at me."

The swimmer said his father had lost about 30kg in six months "which, when you know how much my dad loves to eat, is a pretty frightening thing. But it goes well beyond the physical. It has been a difficult emotional roller-coaster for him."

Le Clos can become the most decorated African male Olympian, topping the three gold and one silver medal of Ethiopian long-distance runner Kenenisa Bekele.

Phelps has qualified for Rio in the 100 and 200 butterfly and 200 individual medley.

The American, who says his fifth Games will be his last, is aiming to add to his record total of 22 Olympic medals.

(Reporting by Alan Baldwin, editing by John Stonestreet and Ken Ferris)