Lord Coe has spoken of his determination to help athletics recover from doping and blackmail allegations and admitted the sport faces a "long road to redemption".
The International Association of Athletics Federations (IAAF) President's comments come ahead of the release of an independent report into allegations of widespread doping among Russian athletes.
The World Anti-Doping Agency (WADA) will release its findings on Monday.
The report, described as a "game changer", is expected to send shock waves through the sport after IAAF's ethics commission brought disciplinary charges against four men, including the son of former president Lamine Diack and the former head of its anti-doping department.
Diack was succeeded as head of the IAAF by Coe at the end of August. He was under investigation by French authorities over the alleged payment of more than one million euros to cover up doping offences by Russian athletes.
Coe today said those developments had left him in "clear shock" and provoked "a great deal of anger and a lot of sadness".
He told BBC Radio Five Live's Sportsweek programme: "These are dark days for our sport but I'm more determined than ever to rebuild the trust in our sport.
"It is not going to be a short journey."
He added: "The day after I got elected, I started a massive review. Understandably, in the light of the allegations that have been made, that review has been accelerated and I am determined to rebuild and repair the sport with my colleagues.
"But this is a long road to redemption."
Coe has said he would prefer "engagement rather than isolation" when responding to allegations against any specific country.
He has also insisted he was not aware of any allegations against Diack until this week.
When asked if he thought the situation would be shown to involve nations other than Russia, he said: "We'll have to wait for the basis of the WADA report tomorrow. It will be interesting to see where they think that scope is.
"We do know we are taking a disproportionate amount of damage from a relatively few number of nations out there.
"The answer is we will wait - I don't know. It may well."