Tour de France director Christian Prudhomme said Friday that Ivan Basso's chances of competing in this year’s edition of the race could be hampered by a failure to resolve the Italian star’s implication in the Spanish doping affair.

Basso and 1997 Tour winner Jan Ullrich were among dozens of cyclists implicated in Operación Puerto, which uncovered an alleged blood doping and doping network run by a doctor, Eufemiano Fuentes, in Spain.

Both riders were among over a dozen banned from racing last year's Tour de France, which also ended in controversy when American winner Floyd Landis apparently tested positive for testosterone after stage 17.

With the absence of a specific law barring doping, Spanish legal authorities said most of those implicated in Operación Puerto have no case to answer, but the UCI has indicated that its investigation into the affair is far from over.

The UCI's bid to get to the bottom of the affair was boosted recently when a DNA test matched blood found in Fuentes' Madrid laboratory with Ullrich, who has claimed he is innocent and since retired from the sport. That proved to be a turning point for Prudhomme, who is determined to avoid the kind of controversy which deflated 2006's edition before it had even started.

"The information from Germany concerning Jan Ullrich has put it (Operación Puerto) right back into the spotlight," Prudhomme told L'Equipe in a front-page story on Friday. "And naturally, the level of suspicion on the riders implicated has been pushed up a notch.

"The German legal authorities attributed nine bags of blood to Ullrich, which shows that in this affair it is possible to find out answers to questions. The sport just cannot allow cyclists who are still implicated in this affair to start the Tour de France if suspicion still hangs over them." After being cleared of the Italian sports authorities of any wrongdoing, Basso - last year's Giro d’Italia champion - was released by his team, CSC. He later joined the former team of Lance Armstrong, Discovery Channel, and would normally be viewed as a hot favorite for this year's Tour, which begins July 7 in London.

Prudhomme said he has already contacted the American team, and the other teams with riders implicated in the affair.

"I can't say any more,” Prudhomme noted. “The teams have promised to get back to us, and if they don't then we will meet with them next week before the Fleche Wallonne (April 25)."

Prudhomme said he hoped the team managers concerned, including Discovery Channel's Johan Bruyneel, would "do what is right for the good of the sport.”

"We will only get to the end of this if we all work in unison," added the Frenchman, who said wants to work closely with the UCI and the World Anti-Doping Agency to get to the bottom of Operación Puerto. "We have outlined to Johan Bruyneel what seems to us the right path to take." Prudhomme suggested the Tour de France, which played a pivotal role in forcing teams to suspend suspect riders from last year's race, would be more forceful this time around if teams do not cooperate.

Asked how he would feel if a rider implicated in the affair turned up at the start line, Prudhomme was unequivocal.

"Before that happens, we will know how to deal with it," he said. "The Tour was sullied last year, and that won't happen again."