The swimming competition of the Athens Olympic Games promises a dream start Saturday as the two ofthe greatest swimming stars are to make their appearances.

The much hyped rivalry between American teenager Michael Phelpsand Australia's sweetheart Ian Thorpe will make this swimming competition one of the most exciting in Olympic history.

Swimming wunderkind Phelps, quadruple world champion in Barcelona last year, will compete in the men's 400m individual medley.

The victory seems to be within his easy reach as he has broken the world record in this event three times starting from 2002.

He last rewrote his own 400m medley world mark in four minutes 8.41 seconds in the U.S. Olympic swimming trials four weeks ago.

The result of the opening day competition will be vital to Phelps' much hyped goal of exceeding Mark Spitz's record of seven gold medals at a single Olympic Games maybe.

The 19-year-old Phelps, rated the world's best all-round swimmer, qualified for six events but he chose to give up the 200mbackstroke considering the competing schedule.

He holds world records in three of them: the 200m and 400m medleys and the 200m butterfly while in the 200m free he faces world record-holder Ian Thorpe and he'll have to get past world record-holding compatriot Ian Crocker in the 100m fly.

It is also not certain that he can clinch berths both in the 4x200m freestyle lineup and the 4x100m medley relay.

Phelps's quest for the 400m medley gold will be challenged by Hungarian Laszlo Cseh, world championships runner-up.

Phelps was pushed all the way in the 400m medley by the European champion in the 400m medley and 100m backstroke before heclaimed the title in world-record time.

But the 18-year-old Hungarian has to compete just recovering from a foot injury.

Cseh underwent an operation on the broken metatarsal bone in his right foot three weeks ago.

Treble Olympic and world champion Thorpe will split the limelight on the day when he swims in his pet event of the 400m freestyle.

The "Thorpedo" nearly missed his chance to defend his title when he slipped off the block and was disqualified from this eventat the national Olympic trials in April.

Craig Stevens later relinquished his spot to Thorpe, who will also compete in the 100m and 200m free in Athens.

The holder of three world records in 200m, 400m and 800m free will be almost sure to anchor in his country's relay events.

Thorpe raced to his peak in 2001 when he stunned the world by winning six gold medals, the most gold medals ever won by a swimmer at a World Championships. In the process he broke world records in the 200m, 400m and 800m free and another with the 4x200m free relay team.

Since then the 22-year-old has become one of the most popular swimming star not only in his country but around the world.

When asked about his rivalry with Phelps, Thorpe said: "I believe he is an exceptional athlete and that he will have a successful Olympic Games.

"But for me just to look at one other competitor isn't right. It wouldn't do justice to the others in the race. I do know, however, it will be a very fast race."

The women's 4x100 free relay will be a close match between the United States, Germany and Australia, who finished one-two-three at last year's worlds.

Sydney Olympic winners the United States will face a tough title-defending campaign against an Australian quartet spearheadedby 100m free world record holder Libby Lenton and Germany led by 200m free world record holder Franziska van Almsick.

The women's 400m individual medley will see the medley queen Yana Klochkova kick off her defending after the Ukrainian bagged both the 200m and 400m medley titles at last year's world championships.