Tokyo's postponed Olympics will go ahead next year regardless of the coronavirus pandemic, IOC vice president John Coates said, vowing they will be the "games that conquered Covid".
The Olympics have never been cancelled outside of the world wars.
Mr Coates said: "The games were going to be, their theme, the Reconstruction Games after the devastation of the tsunami," referring to a catastrophic earthquake and tsunami in northeastern Japan in 2011.
"Now very much these will be the games that conquered Covid, the light at the end of the tunnel."
In a landmark decision, the 2020 Olympics were postponed because of the global march of the pandemic and they are now set to open on 23 July 2021.
But Japan's borders are still largely closed to foreign visitors and a vaccine is months or even years away, feeding speculation about whether the games are feasible at all.
Japanese officials have made clear they would not delay them a second time beyond 2021.
There are signs that public enthusiasm in Japan is waning after a recent poll found just one in four Japanese want them to go ahead next year, with most backing either another postponement or a cancellation.
Mr Coates said the Japanese government "haven't dropped the baton at all" following the postponement, despite the "monumental task" of putting the event back a year.
"Before Covid, (IOC president) Thomas Bach said this is the best prepared games we've ever seen, the venues were almost all finished, they are now finished, the village is amazing, all the transport arrangements, everything is fine," he said.
"Now it's been postponed by one year, that's presented a monumental task in terms of re-securing all the venues ... something like 43 hotels we had to get out of those contracts and re-negotiate for a year later.
"Sponsorships had to be extended a year, broadcast rights."
With much of that work under way, or accomplished, a task force has been set up to look at the different scenarios in 2021 - from how border controls will affect the movement of athletes, to whether fans can pack venues and how to keep stadiums safe.
The group, comprising Japanese and IOC officials, met for the first time last week.
"Their job now is to look at all the different counter-measures that will be required for the Games to take place," said Mr Coates, the long-time president of the Australian Olympic Committee.
"Some countries will have it (Covid) under control, some won't. We'll have athletes therefore coming from places where it's under control and some where it is not.
"There's 206 teams ... so there's a massive task being undertaken on the Japanese side."
Tokyo 2020 chief Toshiro Muto repeated that organisers hoped to avoid a games without spectators, an option that has been mooted given Japan is still limiting audiences at sports events.