Olympics-Athletics-Rollins leads American trio into hurdles final

By Nick Mulvenney RIO DE JANEIRO, Aug 17 (Reuters) - Brianna Rollins, Nia Ali and Kristi Castlin gave the United States a sweep of the three semi-finals in the women's 100 metres hurdles at the Rio Olympics on Wednesday. Rollins led the way and topped the timesheets by winning the opening race in 12.47 seconds ahead of Pedrya Seymour of the Bahamas, whose 12.64 was a national record and the third fastest time of the round. Nia Ali won the second semi in 12.65 and Kristi Castlin the third in 12.63 ahead of Cindy Ofili, who ensured Britain would have two athletes in the final as her sister Tiffany Porter qualified via her time. European champion Cindy Roelder of Germany and Phylicia George of Canada will complete the field for a final left wide open by the absence of four top high hurdlers. Australia's reigning Olympic champion Sally Pearson was forced to withdraw because of injury, while the Beijing 2008 champion Dawn Harper failed to get through the U.S. trials. Kendra Harrison, who broke the world record with a run 12.20 last month, was another victim of the cut-throat United States national championships. World champion Danielle Williams, whose sister Shermaine just missed out on the final after running the ninth fastest time in the semis, hit a hurdle and failed to get through the Jamaican trials. If the absence of that quartet was not reminder enough of the thin line between success and calamity in the event, Nikkita Holder gave another when she hit the penultimate hurdle in the third heat and tumbled head over heels on the track. The Canadian got up to finish the race but was disqualified for falling out of her lane. (Editing by John O'Brien)