The head of the World Anti-Doping Agency (WADA) complained on Wednesday of slow progress by Russian authorities towards making the country's anti-doping agency (RUSADA) compliant with international standards.
WADA president Craig Reedie told a conference that he was "encouraged by the significant progress" made by RUSADA but added it was still taking too long.
"We want to welcome an independent and efficient RUSADA back in from the cold ... it's just a pity it is taking so long for Russian authorities to make it happen," he said.
Reedie said the slow progress was "despite a significant amount of work being carried out by WADA to persuade the Russian authorities to recognize and accept as true the systemic doping scheme as revealed by the McLaren report."
There was no immediate comment to Reedie's remarks by Russia which has repeatedly denied systemic doping.
RUSADA was declared non-compliant in 2015 after a report commissioned by WADA found widespread doping in the country's athletics.
Since then, the International Olympic Committee (IOC) and WADA have launched a string of investigations — including one by Canadian sports lawyer Richard McLaren — to look into the issue which ballooned into the biggest doping scandal in years, engulfing many sports and said to involve more than 1,000 athletes.
After escaping a blanket ban from the Rio de Janeiro Olympics in 2016, Russia was barred from last month's Winter Games in Pyeongchang although more than 100 of the country's athletes were permitted to compete as neutrals.
"The big losers are Russia's own athletes ... future participation of Russian athletes at major sporting events will continue to be put in doubt," said Reedie.
"If WADA cannot declare that Russia has a compliant national anti-doping agency, then the rest of the world will not be convinced that any meaningful change has taken place [and] the suspicion and doubt will continue."