Rogge told journalists the IOC would maintain a zero-tolerance policy towards drug-taking and he believed anti-doping scientists had finally caught up with drug cheats.

"Doping is our number one priority," he said. "We will augment the number of tests in Athens quite drastically.

"The IOC never hesitated to disqualify famous athletes, may I remind you of Ben Johnson.

"We have sent home famous athletes in the last Olympic Games. We will do it in the future if that is needed, there is no doubt about that."

Canadian sprinter Johnson was stripped of his 100 metre Olympic gold in 1988 after testing positive for steroids.

The U.S. has vowed to send a "clean" team to Athens after clamping down on drug-taking. Sprinter Kelli White accepted a two-year ban after admitting taking banned substances and was stripped of her two world championship gold medals.

Triple Olympic champion Marion Jones, who has repeatedly denied taking illegal performance-enhancing drugs, is the focus of rumours following an investigation into the BALCO lab by U.S. anti-doping officials.

BALCO was named by U.S. anti-doping officials as the likely source of the previously unknown designer steroid THG last year.

The development of a test for THG proved a major success in the battle against doping, trapping European sprint champion Dwain Chambers of Britain among others.

"There are times when they (drug cheats) are not a step ahead and I think we are getting there today, and there are other times when all of a sudden new drugs appear for which we have no immediate testing," Rogge said.

"It has always been a game between the gamekeeper and the poacher and mostly the poacher has a bigger advance on the gamekeeper.

"But today I can say we have caught up with the cheats and we have the tests that are needed. In six months or a year's time, maybe a new drug will appear and we will have to work very hard to catch up."

New tests for products such as human growth hormone, synthetic haemoglobin and practices like blood transfusion may be available before the Olympics in August, scientists and Olympic officials have said.

Rogge said the IOC was committing resources to preventing genetic doping, reflecting concerns in the scientific community that advances in biotechnology and gene therapy could produce genetically modified athletes.

However, he said genetic modification in sport was not seen as an immediate threat.