LONDON - Justin Gatlin's win in the men's 100 meters at the World Athletics Championships was "not the perfect script", IAAF president Sebastian Coe said on Sunday.

Gatlin, of the US, has served two suspensions for doping offenses. His victory ruined Usain Bolt's fairytale farewell on Saturday by beating the Jamaican icon in his final individual race.

Bolt finished third, behind 21-year-old American Christian Coleman, whose compatriot Gatlin was loudly booed by the crowd at London Stadium.

"I'm not eulogistic that someone who has served two bans has walked off with one of our glittering prizes. But he is eligible to be here," said Coe, the head of the sport's governing body.

"It's not the perfect script. I thought Usain was very generous with the observations he made. That must have been a bitter event for him to swallow. He was bigger than the moment, and that typifies his career."

Coe reiterated his support for lifetime bans for convicted drug cheats, but used Gatlin's example to illustrate how legal systems worldwide have frustrated efforts to impose more severe punishments.

Gatlin received a two-year ban in 2001 after failing a dope test for amphetamines found in prescribed medication he had been taking since a child for attention deficit disorder. His suspension was later reduced to one year on appeal.

The sprinter then tested positive for testosterone in 2006 and was suspended for eight years, avoiding a lifetime ban in exchange for his cooperation with the doping authorities.

That ban, however, was also halved by an arbitration panel in 2007.

"There have been two bans in the past," Coe said. "One got watered down, which made it very difficult for the second ban. The second time we went for an eight-year ban, which would have, in essence, been a lifetime ban. We lost that."

Efforts to impose lengthy suspensions on doping offenders have often been overturned in courts or by arbitration panels, with appeals sometimes citing inconsistencies with the World Anti-Doping Agency (WADA) code.

WADA only updated its code from January 2015 to allow a four-year ban for first-time offenders, up from two years.

"I would like to see lifetime bans and so would the majority of people in our sport," Coe said.

"I'm not going to close the door on lifetime bans, but we've constantly tried for them and lost."

Reuters