Olympics-Athletics-U.S. and Jamaica set up 4x400 women's relay showdown

By Mitch Phillips RIO DE JANEIRO, Aug 19 (Reuters) - Five-times defending champions the United States and Jamaica, who upset them at last year's world championships, set up what should be a mouth-watering women's Olympic 4x400 relay final after impressive semi-final performances on Friday. Both teams rested key athletes ahead of Saturday's final, aware that their strength-in-depth meant there was no danger of missing out providing there were no baton mishaps. The Americans, who last missed out on gold in 1992, won the first heat by a distance in three minutes 21.42 seconds and Jamaica nearly matched them in the second with 3:22.38. Ukraine, Britain, Canada, Italy, Poland and Australia also advanced for what is likely to be a race within a race for bronze. France and the Bahamas, who set a national record, missed out. (Editing by Ed Osmond)