LAUSANNE, Switzerland (AP) - The International Olympic Committee on Wednesday reasserted the validity of an anti-doping rule that will prevent American runner LaShawn Merritt from defending his 400-meter gold medal at the 2012 London Games.

The IOC executive board and athletes' commission declared their full backing for the rule, which bars any athlete with a doping suspension of at least six months from competing in the following games.

"The athletes made it very clear they support the rule," IOC vice president Thomas Bach said. "The rule applies. It shows the full resolve of the IOC in the fight against doping and demonstrates that Olympic athletes serve as role models worldwide."

The rule was approved at an IOC meeting in Osaka, Japan, in 2007 and went into force just ahead of the 2008 Beijing Olympics.

Merritt, winner of the 400 meters in Beijing, received a 21-month suspension last year after testing positive for a banned substance found in a male enhancement product.

His ban expires in July, meaning he can return to international competition, including possibly at the world championships in Daegu, South Korea.

However, Merritt is ineligible to compete in London a year later because of the IOC rule.

The American arbitrators who banned Merritt have contested the IOC rule, saying it goes against the World Anti-Doping Agency code and amounts to a second punishment. Bach, a German lawyer who heads the IOC's juridical commission, insisted that is not the case.

"We made it clear from the very beginning that it is not a sanction," he said. "It is a condition of participation. The IOC is governing the Olympic Games and has the right to put conditions for participation."

Bach acknowledged the rule could face legal challenges, possibly in the Court of Arbitration for Sport.

"We will see what happens," he said. "We are interested to solve it as soon as possible."

Among others who could be affected by the rule is American basketball star Diana Taurasi, who tested positive for the stimulant modafinil in November while playing in the Turkish women's league.

Taurasi, who helped the U.S. win gold medals at the past two Olympics, could be banned for up to two years.

Also facing a possible London ban is American swimmer Jessica Hardy, who missed the Beijing Olympics after testing positive for clenbuterol. She was found to have unknowingly taken the banned agent in a contaminated food supplement and her two-year suspension was reduced to one.

MELBOURNE, Australia (AP) - Lleyton Hewitt fanned hopes of a hometown win in the Australian Open when he upset Russia's Mikhail Youzhny 7-5, 4-6, 6-4 at the exhibition Kooyong Classic on Wednesday.

Hewitt, ranked 54, beat the 10th-ranked Youzhny in his first appearance at Kooyong to show promising form ahead of the season's first Grand Slam which starts on Monday.

Frenchman Gael Monfils, who tuned up for the Open with a 4-6, 7-6 (5), 6-4 win over defending champion Fernando Verdasco of Spain, was impressed with Hewitt's form and said the Australian can win a Grand Slam this year.

Russia's Nikolay Davydenko beat Czech Tomas Berdych 7-5, 3-6, 6-3 in the third match on opening day.