By Gilles Le Roc'h

PARIS, July 28 (Reuters) Floyd Landis should know by Monday if his B sample has confirmed his positive drugs test in the Tour de France.

The American, with help from doctors and lawyers, faces a tough task in trying to clear his name after testing positive for the male sex hormone testosterone on his way to victory in cycling's most prestigious race.

Anti-doping procedures have become more and more precise and athletes are now rarely cleared on technicalities, although it cannot be ruled out that the counter-analysis requested by the American turns out to be negative.

Many cycling officials have said there should be no mercy if it is confirmed that the Phonak rider has tested positive.

''Our sport's survival is at stake,'' said Patrick Lefevere, the manager of the Quick Step team and the president of the Association of professional cycling teams.

''We can no longer afford to have teams or riders who just won't learn still starting races.'' Landis has denied any wrong-doing and asked for the B-sample to be analysed. The result should be known over the next 72 hours.

If it confirms the positive test, the American federation USA Cycling will have a month to make a ruling, with its most likely decision being a two-year ban.

The Tour organisers, meanwhile, will strip Landis of his crown and declare Spain's Oscar Pereiro, who finished second overall, the winner.

LONG PROCEDURE Landis's lawyers could then take the matter to the Court of Arbitration for Sport (CAS), a potentially long procedure.

On July 20, 30 minutes after winning the Tour's last mountain stage to Morzine, Landis went to the doping control at a mobile home set up by race organisers near the finish line.

There he was met by a medical inspector of the International Cycling Union (UCI) and two doctors appointed by the French Sport ministry.

The medical team supervised how the samples were handled and frozen. The flasks containing Landis's urine samples were then flown that night to an airport outside Paris and conveyed from there to a nearby specialised anti-doping lab.

''The bottles arrive between six p.m. and midnight,'' said lab director Jacques de Ceaurriz. ''We pay guards who put them somewhere safe. We analyse them the next morning when our offices open and we give the results 24 to 48 hours later. It can take up to 96 hours in some difficult cases.'' The lab workers do not look for any substance in particular but screen the samples in search of the 250 molecules on a list which is constantly updated by the World Anti-Doping Agency (WADA).

''If we are alerted that one of those 250 molecules has been identified by the machine, we start a procedure to look for the substance and identify it,'' De Ceaurriz explained.

The lab workers had no way of knowing the positive sample belonged to Landis.

The test result was then communicated to the International Cycling Union (UCI), WADA and the French anti-doping agency. A personal code on the bottle allowed UCI to establish the sample was from Landis.

The ruling body then informed Landis's team and his federation that the rider had tested positive.

Reuters DH RS1858