Olympics chief Thomas Bach revealed he masked his concerns about Tokyo 2020 going ahead because of fears the Games might "fall to pieces".
Bach is president of the International Olympic Committee, which he said "had to show a way out of this crisis" in order for the global event to go ahead amid the COVID-19 pandemic.
Speaking on Tuesday in Tokyo, Bach said the IOC had experienced daily concerns about the Olympics being able to proceed but had to present a positive message to stakeholders including sporting federations, sponsors, the Japanese government and broadcasters.
Had the IOC been open about worries for the Games, which were delayed by a year due to the global health crisis, Bach said it could have triggered a chain of events that would have seen the Olympics collapse.
Instead, the Games get under way this week, with the opening ceremony due to take place on Friday.
Bach said: "Over the past 15 months, we had to take daily decisions on very uncertain grounds. We had doubts every day. We deliberated and we discussed. There were sleepless nights. Like everyone else in the world, we did not know, I did not know, what the future would hold."
Bach appeared to scoff at any suggestion of the IOC deciding to "blindly force ahead at any price" and spoke of the "extreme stress test of the coronavirus crisis".
"Imagine for a moment what it would have meant if the leader of the Olympic movement, the IOC, would have added to the already many doubts surrounding the Olympic Games, if we would have poured fuel onto this fire," Bach said.
"How could we have convinced the athletes to continue to prepare for the Olympic Games by adding to their uncertainty?
"How could we have convinced all the other stakeholders to remain committed to the Olympic Games if we would have even deepened their already serious doubts.
"Our doubts could have become a self-fulfilling prophecy. The Olympic Games could have fallen to pieces. This is why, we had to keep these doubts to ourselves. This today I can admit and say it, it also weighed on us, it weighed on me.
"But in order to arrive at this day today, we had to give confidence. We had to show a way out of this crisis. We had to provide stability. We had to build trust. We had to give hope."
The IOC announced updated COVID-19 case figures for the Games on Tuesday, with 40 confirmed cases involving residents of Japan and 31 affecting those from overseas.