The swimmer has signed a $5 million (£3.2 million) contract to promote Under Armour, a company based in Phelps' home city of Baltimore and who are best known as for their form-fitting, moisture-wicking apparel designed to be worn under sportswear.

Phelps, who has a mega deal with Speedo to promote their swimwear, will wear Under Armour's products outside the pool.

The deal is expected to last beyond the London 2012 Olympics, where Phelps will be seeking to add to his total of 14 gold medals, eight of which were won at Beijing in 2008.

That record-breaking performance put him in the position to be one of the highest earning athletes in the world until he was photographed on the front of the News of the World, Britain's biggest-selling tabloid newspaper, in January last year smoking from a marijuana pipe.

Phelps threatened to quit over the picture, although he soon changed his mind.

He later apologised, calling his behaviour "regrettable" and "inappropriate," and was suspended for three months by USA Swimming.

Most of Phelps' sponsors stuck by him, including high-end watch maker Omega, video-game publisher 505 Games, Hilton Hotels Corp, PureSport, Subway, Visa Inc, automaker Mazda Motor Corp in China and H2O Audio.

His first national TV commercial for Under Armour will co-star UFC welterweight champion Georges St-Pierre, Milwaukee Bucks rookie Brandon Jennings and former Oklahoma State wide receiver Dez Bryant.

Under Armour is best known in Europe for signing a deal in 2008 to supply the team kit for Wales rugby union team.

It also sponsors German Bundesliga team Hannover 96.

They also sponsor Fulham striker Bobby Zamora, who is on the verge of earning a call-up to England's squad for the FIFA World Cup in South Africa later this year.

Under Armour products are also popular with United States troops in Iraq and Afghanistan

Contact the writer of this story at [email protected]


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February 2009: Phelps claims he may quit before London 2012 over drug picture