BEIJING, Aug 13 (Reuters) - Jeremy Wariner's budding rivalry with fellow American LaShawn Merritt has fuelled the Olympic and world 400 metres champion with a new desire to excel, Wariner said on Wednesday.

"For me it's great to have a rivalry," the 24-year-old Wariner told a news conference. "It makes me train harder. When I go to the track I know LaShawn will be there working as hard as I am."