Russia was provisionally suspended as an IAAF member in November following a damning report by the former head of the World Anti-Doping Agency
, Dick Pound, that claimed the country had engaged in widespread and state-sponsored doping.
That suspension could see the Rio Olympics take place without one of the world's strongest track and field teams.
"I have not put a timeframe on that," Coe told CNN's Amanda Davies when asked about the return of Russian track and field athletes to the competition.
"It will be when we are satisfied that the changes have been made are both verifiable and sustainable. This cannot be just a one off change, we have to be sure that these changes are culturally embedded in the sport going forward.
"The timeframe for Russian athletes, clean athletes, (coming) back into the system is very clearly identified in the work that Rune Anderson,
the chair of the independent commission, has just been involved in with the task force in Moscow," Coe said.
Anti-doping expert Andersen has spent the last few days in Moscow meeting Russian officials highlighting the changes the country must make to its anti-doping program and and is due to report back to the IAAF in March.
Corruption, blackmail and collusion
A separate IAAF ethics committee report released last week revealed the level of corruption, blackmail and collusion that went on between senior IAAF and Russian officials to keep positive drug tests secret over a number of years.
Lifetime bans were handed down to IAAF consultant Papa Massata Diack, who is the son of the former IAAF president Lamine Diack, as well as the head of Russia's Athletics Federation and the country's former chief long distance running coach.
The IAAF's former anti-doping director Gabriel Dollé was also given a five-year ban while French prosecutors are investigating the affair.
And allegations of doping keep coming. Documents uncovered by the Associated Press and released on Wednesday
allege the IAAF was aware and concerned about the level of doping, as well the impact it was having on the health of Russian athletes, as far back as 2009.
Coe and his embattled organization are likely to come under further scrutiny when the second part of Dick Pound's report is released Thursday.
Briton Coe wouldn't say whether it will contain more uncomfortable revelations but admitted these were "dark days" for the sport.
However, the IAAF chief insisted it was the actions of a very small number of countries that worried him.
"We know that we have suffered a disproportionate amount of damage from a relatively small number of countries," said Coe.
And Coe refused to rule out further competition bans before the Olympics gets underway.
"If we are not satisfied at the IAAF that the countries that we are looking very closely at are not prepared to make the changes we want then sanctions will follow," he said.
'A sport I owe everything to'
Coe's position at the head of the IAAF has come under intense scrutiny since the scandal was revealed last year.
The former track and field star, who won gold in the 1,500 meter events at the 1980 and 1984 Olympics, was elected head of the IAAF in August 2015 after serving as a vice president at the organization.
Away from doping allegations, questions have been asked about the awarding the 2021 World Athletics Championships to the city of Eugene, Oregon
-- another decision being probed by French prosecutors.
But when asked if he felt regret over standing for the presidency in light of what has come to pass in the period since, he was emphatic.
"Not for one moment and why would I?" he responded.
"This is a sport that I owe everything, the only reason I am sitting here today whether this is an uncomfortable interview or not is because I come from the great sport of athletics.
"The crisis was actually two or three years ago when what we're having to deal with was taking place, our responsibility is now to make those changes and take the sport into safe safe territory.
"My focus every day, every hour of that day is to help shape the future of our sport," he said.