American superstar Michael Phelps hoped to learn lessons from the losses to China's promising swimmer Wu Peng and perform better at the Shanghai world championships.

Phelps has struggled this season to regain the best form, as he lost three times in the 200m butterfly in this year's USA Swimming Grand Prix Series, twice to Chinese Wu Peng and once to Aussie Nick D'Arcy.

"Those races have been kind of frustrating for me a lot this year. I had not been able to perform as well as I'd like to," recalled by the 26-year-old at the press conference one day before the start of the swimming competitions running from July 24 to 31.

The 14-time Olympic gold medallist, who set an unprecedented eight-gold feat at Beijing Olympics, said he and Wu had some pretty good races and the opponent got his best in this season.

"I hope I can be able to learn from those races," said he, adding that he aimed to fix things here and perform better. The Ameriacn talent also showed his confidence in the fly, saying his feeling was pretty good and was relaxed before the race.

Bob Bowman, the coach of Phelps, said the Championships was the stepping stone for next year's London Olympics.

"This week is the beginning of our preparations for Londdn Olympics." said the coach, adding that what ever happened in Shanghai was what they sought to set table for Phelps' last Games.

Phelps, who collected five golds in the last worlds, might swim in seven disciplines including 100m and 200m butterfly and some relays in Shanghai.