Watch Phelps win 100m butterfly at December's Duel in the Pool in Manchester
American swimming legend Michael Phelps says the London Olympics in 2012 will be his final Games and that he will quit the sport when he turns 30.
The most prolific Olympic gold medallist of all time, with 14 to his name, will be 27 in 2012.
"I told myself I will not swim over the age of 30 and I will not," he said.
Phelps has not specified how many races he will enter in London but hopes his refusal to wear the now banned high-tech suits will give him an edge.
He said: "Swimming is going to be swimming again, it's not going to be who is wearing what suit."
Phelps was a bitter opponent of the use of high-tech swimsuits at the World Championships in Rome in 2009, where he lost his world 200m freestyle record to Germany's Paul Biedermann.
The sport's world governing body Fina has since banned the suits and Phelps says it will be "interesting" to see how competitions will go.
He added: "You're really going to be able to see who wants to work and who wants to make sure who stays on top."
Phelps, who is in the middle of a flying visit to the Winter Olympics, won six gold medals at Athens in 2004 and a further eight in Beijing in 2008.
He ruled out entering eight races in London but plans to use this year's Pan Pacific Championships in California and the 2011 World Championships in Shanghai to experiment with different combinations of events ahead of the Games.
"I don't even know," he said when asked how many races he would enter in London. "But I will say it's not eight, I'll give you that one."