MADRID, Spain — World anti-doping officials adopted a revised set of rules and sanctions Saturday, including stronger penalties for aggravated offenses and reduced punishments for athletes who help authorities catch other drug cheats.

The new World Anti-Doping Code was approved on the final day of a three-day international conference on fighting performance-enhancing drugs in sports. It will go into effect on Jan. 1, 2009, after sports bodies have had time to implement them.

"This is an ongoing process," outgoing World Anti-Doping Agency president Dick Pound said. "Nobody thinks the code we adopted today is the final word or the perfect way of dealing with it, but it's a big improvement on what we had. ... It sends a message to the public that we remain firm in our resolve."

The WADA code, which first went into effect in 2004, is the centerpiece of harmonized drug-testing rules across all sports and countries.

Among the most significant changes is the rule allowing for a four-year suspension — rather than the standard two-year ban — for a first doping offense in the event of "aggravating circumstances."

That would include cases of athletes using or possessing multiple banned substances or being involved in a large doping scheme. It also deals with cases where the performance-enhancing effects remain in the body for more than two years, which could cover certain steroids.

The new code also includes incentives to alert authorities to doping violations or to admit doping. A ban could be reduced by 75 percent for any athlete who assists officials in finding other cheats, and admitting to drug use before testing positive would cut a potential ban up to 50 percent.

Also, athletes will be considered guilty of a doping violation if they accumulate a combination of three missed tests or failure to provide information of their whereabouts within an 18-month period. Athletes can be suspended immediately after a positive A sample.