Champion US swimmer Michael Phelps says he's ready for the London Olympics. "It's the most excited I've been since Beijing," he said. Carlo Allegri / Reuters

Olympic swimming great Michael Phelps has regained his passion for the sport he dominated in dazzling style at Beijing, and said on Wednesday he's eager to shine again at the London Games.

Phelps graded himself at "seven out of 10" in his preparations - a big improvement over 2011 but still with "a lot of things that need to change" before the Olympics, which start in London on July 27.

"I'm excited. It's the most excited I've been since going to Beijing," said the 26-year-old, who was in Manhattan for the launch of the "Wash in Confidence" campaign of sponsor Head & Shoulders shampoo.

Phelps won an unprecedented eight gold medals at the 2008 Games to take his career total to 14 Olympic golds and two bronze.

He said then that he wanted to raise the profile of swimming and he did - but the massive attention proved a double-edged sword when a British tabloid published a photo of him appearing to smoke marijuana.

As the Beijing glow faded, he struggled to find the motivation to train.

"It probably took two, two and half years to find it, and it's hard to put the finger on exactly what it was," Phelps said. "There was no passion involved, there was no excitement."

Something clicked, Phelps said, at last year's World Championships in Shanghai.

"Something relit the fire and I was able to get motivated, to get ready," he said.

In London, an in-form Phelps could surpass the record of 18 Olympic medals won by Soviet gymnast Larisa Latynina in three Games - 1956, 1960 and 1964.

"It's crazy because I didn't even know until a week ago when somebody just told me," said Phelps, adding that, as always, he will be working toward the personal goals he has established for himself - not the record books.

"If I can accomplish these goals, I'm satisfied," he said. "It's not about the medals and the records, it's about 'Did I do everything that I put my mind up to do?'"

Those precise goals, like the exact list of events he will aim for in London, remain private, shared only with his longtime coach, Bob Bowman.

"I know what I want to do, but nobody else can know it," he said. "There's only really one person that ever knows my goals and it's my coach. My mom doesn't even know. We are very secretive," he said with a laugh.

On Sunday, Phelps plans to head to a three-week training camp in Colorado Springs. June will bring the all-important US Olympic trials in Omaha, Nebraska.

"Everything can happen," Phelps said. "The only thing I'm looking to do is to try to prepare myself as best as I can for that moment and that day."

While 2012 has seen a surge of comeback attempts by veteran swimmers, including Australian Ian Thorpe and American Janet Evans, Phelps sees London as his Olympic swansong.

"It's a good feeling but it's a weird feeling," he said. "But I'm ready to take the next step, try a couple of other goals I have out of the pool."

That includes travel - and seeing sights beyond hotel rooms and swimming pools in some of the many cities he has already visited.

It will also include his foundation to promote swimming and a healthy lifestyle and, perhaps most importantly, a chance to be unfettered by the constant demands of training.

As for his new publicity campaign based on the importance of having the confidence to win, Phelps says the support of his sponsors, friends, family and fans "is very special and a big part of my success".

"Michael is an icon not only in the United States but all around the world," said Hanneke Faber, a Procter & Gamble vice-president in charge of hair-care products, who said the company will make donations to the swimmer's charitable foundation for every "like" the campaign receives on Facebook.