A man on a mission or a glutton for punishment? Whatever the answer, the swimming world has not seen the last of Michael Phelps [Images] by a long way yet.

After winning an unprecedented eight golds medals in Beijing [Images], Phelps might easily have been tempted to throw in the towel and start spending the millions of dollars flooding his bank account, but the 23-year-old American has no intentions of quitting.

He wants to swim for at least another four years to compete at the 2012 London [Images] Olympics [Images] and has not ruled out the prospect of trying to better Beijing by going for nine medals next time.

• Phelps's great haul of China

"I won't say anything is impossible," he told Reuters in an exclusive interview organised by his sponsors Visa at Beijing's 120-year-old Prince Jun Palace on Monday. "I really don't know what my programme will be, but nothing is impossible."

Having spent the last year churning through thousands of laps to get in shape for Beijing, Phelps is planning to take the next few months off to re-charge his batteries, travel the world and catch up with his friends back in Baltimore.

However, his coach Bob Bowman has already warned him that serious training starts before dawn on New Years Day and he had better be in shape.

"I probably won't be able to sit around for too long. I always want to be constantly moving and exercising," he said.

"I'll definitely try and stay in some kind of shape but nothing big until January or February."

Phelps's next major assignment is the 2009 world championships in Rome where he plans to unveil a new programme that could lay the foundations for his 2012 London schedule.

Phelps has swum the same eight events at the last two Olympics, winning six gold and two bronze medals in Athens, but wants to experiment with different events before London.

He has still not decided which races he will compete in at Rome but told Bowman he wants to drop the 400 individual medley, a gruelling event that requires long hours of training in all four strokes, and focus on backstroke and freestyle sprints.

"My mum told me she wants to go to Rome so I better make the team," he said.

"We're going to play around over the next few years and incorporate some new events and see how they work.

"I'd like to try a few backstrokes and 100 freestyle more... it'll be fun to race (specialist sprinters) Eamon (Sullivan) and Alain (Bernard).

"Those guys are moving so fast through the water so to get in there and race the best is what I'd like to do."