Olympics organisers vowed on Friday to conduct the toughest doping tests of any Games in Athens next year.

They said the latest techniques for catching drug cheats would be transferred to Athens as a priority.

With the sporting world rocked this week by the identification of a previously undetectable drug, Athens organisers (ATHOC) and the International Olympic Committee (IOC) said there would be no compromises in the drug fight, even if it meant leaving sport's biggest event next August without top athletes.

"We are the first ones to want clean Games," ATHOC chief Gianna Angelopoulos told reporters. "We are the ones who want our Games to shine, we have done everything possible in preparing for anti-doping.

"We will strictly follow the rules of the International Olympic Committee and the World Anti-Doping Agency."

While refusing to speculate on the damage the latest crisis could cause to next year's event, IOC chief inspector Denis Oswald, in town to monitor preparation for the Games, said: "This shows that the fight against doping is efficient and we will use the best technology to trace the drugs.

"Stars...if they take drugs, they are not stars."

Four unnamed U.S. athletes and Britain's European champion sprinter Dwain Chambers are confirmed as having given positive 'A' sample urine tests for the previously unknown steroid tetrahydrogestrinone (THG).

US, British, German and Greek sports authorities have started re-testing thousands of samples dating back months to try to identify the extent of the performance-enhancing drug's use.

"The (THG testing) technique is not a new one, but it is different to known techniques. This technique will be transferred immediately to all IOC-accredited laboratories and as a priority to the Athens laboratory," Oswald said.

"Science is making progress and the gap between the cheats and science is getting very narrow...we will make every, every, effort to test the athletes and to make sure the cheaters will not take part in the Games.

"We will...have the best possible equipment in Athens to have the confidence the Games will be clean."

Athletes taking THG face a two-year suspension from all competition and a life-time ban from the Olympics. The drug was considered untraceable until a few days ago.