THE head of the World Anti-Doping Agency "hopes and prays" that the 100-metre final is free of doping incidents so the credibility of sport can be restored.

Agency chairman John Fahey said public confidence in the purity of sport had eroded and there was a suspicious public after the dramatic drug positive of Ben Johnston at the Seoul Olympics and reinforced by the fall from grace of Sydney Olympic sprint queen Marion Jones, in jail for lying about her drug activities.

Mr Fahey said: "I hope and pray this year there is no incident of that nature.

"We must get back to that (having a clean event) or else we are morally bankrupt. I want to change the culture and restore the confidence."

Mr Fahey said there would be drug taking at the Olympics but warned athletes that if they thought they could get away with it "it is less likely than before".

He said the agency had collaborated with authorities to ensure there was comprehensive targeted testing of athletes before the Games and the recent spate of positive tests were the product of that strategy. "It is naive for us to think there will be no doping during the Games. We can be sure that with the progress of the last four years that the cheats stand a far greater chance of being caught," he said.

But Mr Fahey said he was confident that genetic doping would not occur at Beijing.

He said it was critical to restore public confidence in the drug-testing process because there were sports at risk of disappearing. "A sport will wither if the public marches with its feet and the sponsors withdrew their sponsorship. So there is little doubt sports have to take their part very seriously," he said.

Agency chief executive David Howman said the agency and the world athletics body the International Association of Athletics Federations may pursue any evidence of systemic doping within Russian track and field, following the suspension of seven female athletes for urine manipulation late last month.

Mr Howman said if anyone in the athletes' entourage or with jurisdictional authority at the sport or government level was proven involved, the agency would encourage sanctioning.