Challans, France ? Lance Armstrong, ever the headstrong Texan, aims to succeed where the likes of Michael Jordan, Muhammad Ali and other sporting giants failed.

Ali fought well past his prime. And Jordan will not be remembered for his lackluster final season with the Washington Wizards, when he played even as his magic touch seemed to be fading.

But Armstrong could, at the Tour de France that starts today, achieve an oft-elusive feat in sports by walking away at the top of his game.

Already the only six-time winner of the grueling and storied three-week cycling marathon around France, Armstrong wants to start his retirement by wearing an unprecedented seventh champion’s yellow jersey when he crosses the finish line in Paris on July 24 after 2,242 miles.

“I feel excited and obligated to win,” Armstrong said earlier this week.

Such a victory would mark a triumphant end for the 33-year-old who first conquered cancer before defeating all-comers on French roads and mountain passes.

A loss, meanwhile, would mark a decisive beginning to the post-Armstrong era for cycling and for the Tour, its showcase event and arguably the most arduous of all sporting challenges.

UPDATE UPDATES STYLES; Graphics give detailed info on stages 1 through 10 of the Tour de France; with related stories; 1c x various; 47 mm x various

Armstrong’s string of success since 1999 has helped rejuvenate the venerable 102-year-old race, drawing new audiences beyond cycling’s traditional fan base in Europe.

For the first time this year, the race is being broadcast live in Australia. China and India are getting television coverage, too, all of which should help ensure that the Tour continues to thrive long after Armstrong hangs up his bike.

For his rivals, this Tour offers one last chance to make history as the rider who ended Armstrong’s reign.

Jan Ullrich, the 1997 winner who since has finished runner-up to Armstrong three times and who placed fourth last year, came to race this time with an aura of menacing confidence, looking lean and fit.

“This is the last time I can beat him, so naturally it is an extra motivation for me,” the German said.

Ullrich also has a strong team of support riders, including the aggressive Alexandre Vinokourov from Kazakhstan, who finished third in 2003 and is eager to make his mark again after missing the Tour last year through injury.

Ullrich’s challenge got off to a bad start when he crashed into the back window of a team car Friday during a training run. His T-Mobile team press officer Luuc Eisenga said Ullrich had minor cuts and scratches on his neck but will be fit to start today.

Ivan Basso, the ever-improving Italian who was the only rider to stick with and even beat Armstrong up the exhausting, winding climbs in the Pyrenees last year, also could be a threat but has yet to prove that he has the killer alpha-male instinct that the American has in spades.

Outsiders include lithe Spanish mountain riders Roberto Heras, a former Armstrong teammate, and Iban Mayo. But they both failed to live up to expectations last year.

Since Armstrong secured his sixth crown in 2004, surpassing the previous record of five victories he shared with Spain’s Miguel Indurain, Frenchmen Jacques Anquetil and Bernard Hinault and Belgium’s Eddy Merckx, some have questioned whether he is fully motivated this time round.

But such speculation seems to ignore the competitive fire that burns naturally in Armstrong. Just winning, whether it be for the first time or the hundredth, is for him motivation in itself.

Surviving cancer also steeled him, both physically and mentally, for the Tour’s rigors.

“What it teaches is this: pain is temporary. Quitting lasts forever,” he says.

Basso, for one, has no doubts that Armstrong remains the man to beat.

“Of course he’s still hungry. When a rider wins six Tours, he’s not a normal person in the head,” said the CSC team rider, who at 27 is just coming into his prime.

Today, the 189 riders go out individually in a flat-out pedal against the clock over 11.8 miles from the Atlantic Coast town of Fromentine to the island of Noirmoutier-en-l’Ile.

The wind-swept course, while longer than has been usual for the first day of recent Tours, is still too short for the favorites to open decisive time gaps over each other. Nevertheless, it will be an early test of form.

Armstrong, wearing the colors of the Discovery Channel that took over sponsorship of his team after last year’s victory, will set out last, an advantage because it allows him to see how other riders fare first.

He’ll ride a sharp new-look bike decorated by New York graffiti artist Lenny Futura and engraved with the numbers “10/2” – to mark the day, Oct. 2, 1996, when doctors informed him he had testicular cancer.

Armstrong has since called anniversaries of that date his “Carpe Diem Day.” The Latin phrase means “seize the day” and also could be used to neatly sum up the way in which Armstrong consistently struck at key junctures on previous Tours, hammering rivals on mountain climbs and time-trial races against the clock.

Following today’s prologue, the Tour heads eastward to Germany before hitting the Alps, the Pyrenees, and the Massif Central in central France where a time trial on the penultimate day will decide the final placings before the traditional victory ride into Paris.

There, win or lose, Armstrong will say goodbye.