Lord Coe concedes it's impossible to stamp out drug cheats
There can be no guarantees of a drug-free World Championships next month because "people will always seek to cheat", according to Lord Coe.
The president of world athletics' governing body the IAAF insists anti-doping efforts have improved massively but feels it is almost impossible to stamp out cheating completely.
"It's a very utopian view, people will always seek to cheat," Coe said.
"I would love to tell you that we will have a drug-free sport in future. Everything we are doing is engaged in trying to achieve that but we know a few people will cheat.
"What we do have in place now is an independent athlete integrity unit, we have independent sanctioning and discipline and we will be able to be a lot tougher and speed up the process."
Russian athletes will be banned from the championships in London having been suspended by the IAAF over allegations of state-sponsored doping.
The championships will mark the end of Jamaican sprint star Usain Bolt's career on the track, as the eight-time Olympic champion prepares to head into retirement.
Coe admitted the sport has a tough job on its hands to make up for his absence.
"He fills a room, he fills a stadium, and our sport is going to have to work hard to make sure the world recognises that it's not just about Usain Bolt," he said.
"It's a bit like (Muhammad) Ali (retiring from boxing) - you don't replace Ali."