In final Tour de France appearance, 7-time Tour champion Lance Armstrong takes aim at former Astana teammate Alberto Contador.

Lance Armstrong is giving the Tour de France one last go, and two-time winner Alberto Contador is the man to beat again when the three-week cycling extravaganza starts on Saturday.

The Tour goes on under the near-perennial doping cloud, but with a rivalry between former teammates Armstrong and Contador now in the open, their race will hopefully overshadow any drug cheats during this 97th Tour.

The nearly 200 competitors will start not in France but in the Dutch port city of Rotterdam on a 3,642-kilometer (2,263-mile) trek across Belgium, then clockwise around the French north, east and south before heading up to Paris for the finish on July 25.

Aside from the short prologue, organizers have scheduled only one individual time trial on the next-to-last race day. The course layout offers a bouncy and bracing run over cobblestones, and treks through the Pyrenees that will be crucial to the outcome.

The sport has already had another bumpy ride this year.

Swiss star Fabian Cancellara has been hounded by repeated questions about whether he used an imperceptible motor in his bike frame while winning the Paris-Roubaix race - claims he has denied as ridiculous. But the International Cycling Union, or UCI, will deploy a scanner to help make sure such contraptions aren't on hand at the Tour.

Armstrong - by far cycling's biggest star - has been on the defensive over doping allegations from former teammate Floyd Landis, the fellow American who was stripped of his 2006 Tour title for cheating.

The 38-year-old Armstrong, who'll be seeking an eighth victory at his 13th Tour, has had other knocks. He crashed out of the Tour of California, and two bouts of sickness disrupted his training plans.

In recent weeks, he has showed impressive, if not spectacular, form: He placed third at the not-so-difficult Tour of Luxembourg, and second at the mountain-rich Tour of Switzerland.

Contador, who stayed with Astana after Armstrong bolted last year to join Team RadioShack, looks nearly invincible. He won the Paris-Nice, the Tour of Algarve and the Vuelta de Castilla and Leon, and placed second in the Criterium du Dauphine.

Taking a page out of Armstrong's old playbook, Contador has limited his racing days this year to focus on peaking for the Tour.

Armstrong knows his work is cut out.

"It will be very hard to win the Tour," he said this month at the Tour of Switzerland. "With my age, and the explosiveness of the other guys, my own struggles with the time trials in the last couple of years ... We'll have to be smart, to be a bit lucky, to play the team card a little bit.

"There are a handful of guys who are bigger favorites than me."

He could have been talking about the Schleck brothers, Frank and Andy; Ivan Basso, the Giro d'Italia champion; and Cadel Evans, who twice placed second at the Tour de France. Longer shots include Russia's Denis Menchov, Britain's Bradley Wiggins - fourth at last year's Tour - and Kazakh star Alexandre Vinokourov. Or perhaps Cervelo TestTeam's Carlos Sastre.

The race celebrates its 100th year in the Pyrenees, with four rides through the mountains on the French-Spanish border. There is a twin billing of the dreaded Tourmalet pass - including an uphill finish on it in Stage 17.

Among other race highlights will be Tuesday's Stage 3, featuring a total of 13 kilometers (8 miles) of bone- and bike frame-jarring cobblestones.

Among sprinters, keep an eye on Britain's Mark Cavendish. He won six stages last year but wants to take home the best sprinter's green jersey, which has eluded him in each of his last three Tours.

U.S. rider Tyler Farrar will be looking to make his mark in that discipline along with veterans such as Australia's Robbie McEwen, Spain's Oscar Freire and Norway's Thor Hushovd.

For an event where so many stars have been caught doping, linked to drugs scandals, or hounded by persistent suspicion about cheating in recent years, the 2009 Tour appeared relatively clean.

The only positive test last year was on Mikel Astarloza of Spain, whose system turned up endurance-booster EPO. He had won the 16th stage.

France's anti-doping agency accused the UCI of lax controls at last year's Tour, sparking a new, bitter feud between the two sides - and ending their cooperation on anti-doping checks.

Because of that squabble, this year the World Anti-Doping Agency will fill the void left by the French agency and deploy six independent observers to keep watch on the UCI's doping controls.

Race organizers say UCI's biological passport program and hard penalties are helping to curb doping in the peloton and deter cheats.

"Without being a 100 percent guarantee, it's clearly an improvement compared to what was done in the past," said Tour director Christian Prudhomme in an interview with French sports daily L'Equipe. "I'm convinced there has been a real step forward."

Armstrong remains in the crosshairs about doping. French prosecutors say his 2009 Astana team is facing a preliminary investigation after the discovery of suspicious syringes during the race. That probe is ongoing.

Landis dropped a bombshell in April, accusing Armstrong of doping, teaching other riders to cheat, and paying off a top sport official after allegedly testing positive in 2002. Armstrong has denied Landis' claims.

U.S. officials are investigating the claims, and the UCI has asked members in four countries to do so, too.

Despite all of that, Armstrong is focused on the Tour - which will be his last, according to a post he made on his Twitter page this week.

He doesn't seem to be stressing out about it, and is thinking of his wife and four - soon to be five - children. And putting his illustrious career in perspective.

"I have to be happy: 39 years old, I've been doing this for 17 years, and I'm still at the front," he said. "Despite the (expletive) that I read in the newspapers, and on the Internet everyday, about people talking about me, the record speaks for itself.

"These days I don't get too nervous. I'm pretty comfortable in my life right now. If I'm 20 minutes down, I'm still going to go home and have five kids jumping all over me."

But for now, he wants to get a jump on Contador and Co.

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