There is still "a wall of denial" within Russian athletics and its federation is not doing enough to prove it is ready to participate at this summer's Olympic Games in Rio, Dick Pound has said.
The Russian athletics federation was suspended from all international competition for doping offences in November after a meeting of IAAF council members.
Pound, chair of the World Anti-Doping Agency's independent commission, speaking at the Tackling Doping in Sport conference in London on Wednesday, said: " Even with the presence of credible evidence, there was, and to some extent there still is a wall of denial.
"Russia, in the sport of athletics, is on the outside trying to get back in. The onus is on it to justify any readmission.
"It is also clear that opinion is divided on the matter of readmission. The Russians seem to assume that the controversy will disappear and there should be no question regarding their participation in Rio. No question.
"In other parts of the sporting world there is great resistance to any fast-track solution."
Pound, who thought it was "unlikely" that the suspension of track and field athletes would be extended to other sports in Russia, added: "We said (to the Russian athletics federation) 'here are some of the findings you are going to be facing. If you want to get back in you have got a steep hill to climb, but i f you devote all of your resources and attention to solving the problem instead of solving the report you have got a chance to do it in time for Rio'.
"I don't think they are devoting all their time and energy to where they should be to getting, or where thy ought to be. They really have got to address the issues.
"It is a considerable hurdle for them and if the two organisations (WADA and the IAAF) are not satisfied that the clean competitors of the Games are protected then my guess is that they may not make it back for Rio."