Sebastian Coe has said he wished he did more to stamp out doping while a vice-president of athletics' governing body.
The double Olympic gold medal winner said now he was president of the International Association of Athletics Federations (IAAF) he would not "pass up" the chance to effect change.
In an interview with ITV News Sports Editor Steve Scott, Lord Coe denied senior figures at athletics' governing body knew the full extent of doping by Russian athletes.
He also said he would look at erasing some world records as a result of cheating in the sport.
Lord Coe, who headed the successful London 2012 bid, said it would have been difficult to intervene further during his time as IAAF vice-president, from 2007 to 2015, because of other investigations taking place.
But he admitted: "I wish we had reduced the walls. Should we have intervened earlier? Possibly, but it's difficult to see how."
He added: "As president I now am in a position to effect that change and I'm not going to pass up on that chance."
Lord Coe spoke ahead of the publication of a new World Anti-Doping Agency (WADA) report on Thursday. Last week, three officials were banned for life after it emerged IAAF staff tried to cover up doping.
He said all athletes who were caught doping were sanctioned but the scale of cheating was not made clear.
He said there were executive level discussions of the growing problem, but "the walls were clearly too high", adding: "Those are the types of concerns that should have been expressed clearly to the council."
Asked whether he was concerned more countries could be outed in Thursday's report, Lord Coe said his "instincts" were that the problem was limited to those who have already been banned.
But he said he would not be afraid to bring sanctions against any nations found to have cheated.
"There may be other countries that are mentioned and if there are we will meet that challenge," Lord Coe said. "The overwhelming principle here has to be to get the cheats out of the sport as quickly as we can."
The IAAF chief also said suspect world records could act as a barrier to some athletes entering the highest levels of the sport, but did not specify which events or distances he was referring to.
"I have for a long time been concerned about some of those records," he said.
"The chances of matching that world record are probably, I believe, an inhibitor."