ATHENS, Greece — The IOC ratified a new rule today to keep convicted doping cheats out of future Olympics.

Under the regulation, athletes will be banned from the following Olympic Games if they received a drug suspension of at least six months in the previous four-year period.

The rule goes into effect on July 1 and will first apply to eligibility for the 2010 Winter Games in Vancouver, followed by the 2012 Summer Olympics in London.

The ban is not retroactive and does not affect eligibility for the Aug. 8-24 Beijing Olympics.

"Should an athlete get caught doping in Beijing and then get a sanction of six months, he will not be eligible for the 2012 London Games," IOC spokeswoman Giselle Davies said.

The rule would cover athletes caught using steroids, EPO and other serious performance-enhancers.

The proposal was first announced by International Olympic Committee president Jacques Rogge in August 2007 at the world athletics championships in Osaka, Japan.

Rogge had said the change would need to be formally ratified by the full IOC assembly at its session in Beijing this August.

However, because the rule applies to eligibility and not sanctions, it was endorsed earlier by the 15-member executive board, Davies said.

By taking the action now, the IOC is determined to send a message ahead of the Beijing Olympics, where around 4,500 doping controls will be conducted.

"The IOC has a clear position — zero tolerance," Davies said. "The decision taken today is a step to ... reinforce and find another weapon in the armory in the fight against doping."