TOKYO (REUTERS) - Australia's Cate Campbell underlined her status as favourite for the 100 metres freestyle gold at the Rio Olympics when she matched her world-leading time of 52.38 seconds at the Japan Open.

The 24-year-old London relay gold medallist has been in strong form this year and eclipsed her injury-hampered younger sister Bronte, the reigning world champion in the blue riband sprint.

Her time at Tokyo's Tatsumi International Swimming Centre late on Saturday matched the one she swam at the Australian Olympic trials in Adelaide in April, which was the fifth fastest of all time.

Bronte was third in Tokyo but is still the second-fastest woman over the distance this year, her 52.58 at the Australian trials keeping Sarah Sjoestroem (52.78) in third place on the 2016 time sheets.

Sjoestroem is looming as the greatest threat to the Campbell family's hopes of gold in Rio and the Swede coasted to 100m freestyle victory in the European championships in 52.82 on Wednesday.