Swimming, perhaps for the first time, is threatening to trump athletics as the main attraction at the Athens Olympics, thanks to Michael Phelps and Ian Thorpe.

The pair are bidding for places in swimming immortality by tackling two of the sport's greatest records and their clash promises to be the highlight of the August 13-29 Olympics.

Phelps is aiming to better Mark Spitz's record of seven gold medals at a single Olympics while Thorpe, who already has three gold medals from Sydney four years ago, is chasing Spitz's career tally of nine.

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Phelps surpassed Thorpe as the number one swimmer by setting five world records and winning four gold medals at last year's world championships in Barcelona.

But the American teenager has his sights set even higher in Athens, contemplating a gruelling schedule that would make him the greatest Olympian of all time.

He has entered the 100 and 200 metres butterfly, the 200m and 400m individual medley, the 200m freestyle and the three relays.

It is a challenge that seems almost too much to contemplate but Phelps's astonishing efforts at the world championships raised expectations.

The 19-year-old Phelps also qualified for a ninth event in Athens but dropped the event for fear of overloading himself.

His gruelling programme caught up with him in Barcelona last year when he was beaten by his team mate Ian Crocker in the 100m butterfly final and the competition will be even stiffer at the Olympics.

HISTORY BECKONS

Thorpe looms as the man most likely to ruin Phelps's bid for eight golds. The Australian, voted the best male swimmer in the world four times between 1998 and 2002, had also flirted with the idea of tackling seven events in Athens but abandoned his plans last year.

The Australian, who won six gold medals at the 2001 world championships in Japan and the 2002 Commonwealth Games in Manchester, decided to focus his energy on six races.

But history still beckons for the 21-year-old Thorpe, who is entered for the 100m, 200m and 400m freestyle and the three relays. No one has ever won the freestyle treble and if he wins six gold medals he will match Spitz's career tally.

Thorpe and Phelps will go head to head in the three relays plus the 200m freestyle, which promises to be the race of the Olympics.

Thorpe's ambitions were almost sunk when he was disqualified from the 400m at the Australian trials in March for a false start.

Unbeaten in the event for seven years, Thorpe was thrown a lifeline only when his team mate and friend Craig Stevens pulled out to concentrate on his other events, clearing the way for Thorpe to defend his Olympic title.

Phelps and Thorpe are not the only ones chasing history in the Greek capital. Russian Alexander Popov, now one of the sport's veterans, showed his younger rivals a clean pair of heels when he won the 50m-100m freestyle double at the world championships.

Popov won the sprint double at the 1992 and 1996 Olympics but had to settle for silver behind Dutchman Pieter van den Hoogenband in the 100m at Sydney and missed a medal in the 50m.

Now 32, Popov has the chance to become the first swimmer to win individual medals at four Olympics if he can get on to the podium in Greece.

YOUNGER RIVALS

Van den Hoogenband won the 100m and 200m in Sydney but has been unable to reach such heights again, failing to win either event at the 2001 or 2003 championships. He lost his 200m world record to Thorpe three years ago but still retains the 100m mark.

Van den Hoogenband's team mate Inge de Bruijn was the outstanding female swimmer in Sydney, winning three individual titles, but she is under siege from her younger rivals.

She won the 50m freestyle crown in Spain but lost her 100m freestyle world record to Queensland teenager Libby Lenton during the Australian trials.

Lenton's compatriot Jodie Henry also equalled de Bruijn's old mark, giving Australia the two top-ranked female sprinters in the world and threatening the U.S. dominance of the relays.

America's premier female swimmer is Natalie Coughlin, a Californian university student who also competes in backstroke and is entered for five events.

History shows that only a rare few swimmers win individual titles at different Olympics but there are two champions from Sydney who show no signs of slowing down.

Australia's Grant Hackett, the undisputed king of the 1,500, remains as dominant as ever in his pet event and Ukraine's Yana Klochkova continues to set the pace in the women's medley races.

The United States once again loom as the most powerful swimming nation with Australia the next best. The U.S. boast the current world record holders in eight of the 13 men's individual events.