TOKYO: Japanese swimming star Kosuke Kitajima has warned against any complacency in his defense of the double Olympic breaststroke titles after US rival Brendan Hansen failed to qualify for the 200m race.

"It was unfortunate, indeed," Kitajima said of Hansen's flop as he returned home from a month of altitude training in Flagstaff, Arizona, Japanese dailies reported Wednesday.

"They say I am favored. But there is no change in my determination to achieve my goal without fail," the 25-year-old Kitajima told reporters at Tokyo's Narita airport on Tuesday.