By Karolos Grohmann
RIO DE JANEIRO (Reuters) - The International Olympic Committee (IOC) will continue pushing for a lifetime ban of doping offenders despite having failed twice to keep past drugs cheats from competing in the Olympics.
IOC President Thomas Bach "started his career in sports administration... calling for lifetime bans," said IOC spokesman Mark Adams on Saturday. "He still believes in lifetime bans and would like to push towards that."
The IOC attempted to block Russian athletes with a doping record from competing at the Rio Olympics as part of wider efforts to sanction Russia over state-backed doping.
But their effort was thwarted by the Court of Arbitration for Sport (CAS), which ruled athletes cannot be sanctioned twice.
The IOC had also attempted in 2011 to pass the so-called "Osaka rule," where athletes with a doping sanction of six months or longer would be automatically ruled out of the next Games, but that was also blocked by CAS.
"We have tried on a couple of occasions. Unfortunately the Court of Arbitration for Sport didn't want to be as tough as us and we understand that there are legal reasons why we can't be," said Adams.
"But we will certainly go away and think and see a way we can do that, where serious doping offences lead to a lifetime ban."
As things stand now, athletes caught doping could face a four-year ban but after serving it are eligible to compete in any international event, including the Olympics.
U.S. track and field medal hopefuls Justin Gatlin and LaShawn Merritt are among several high-profile drug offenders in Rio.
National Olympic committees can also not exclude athletes based on past doping offences, with the British Olympic Association's (BOA) own lifetime ban from the Olympics shot down by CAS before the London Games.
The BOA had attempted to block sprinter Dwain Chambers, but the athlete won at CAS and competed at the London Olympics in 2012.
"It has to be done in a legal framework that is acceptable otherwise you will see that we will be told by the Court of Arbitration for Sport that is not acceptable," Adams said.
"The president (Bach) remains very firm in his belief that that's something we would like to push towards. Whether it's achievable in the legal framework, we will have to see."