Thomas Bach says the Olympic Games could have "fallen to pieces" if the International Olympic Committee had not taken the unprecedented decision to reschedule as a consequence of the coronavirus pandemic.
The IOC president insisted outright cancellation was "never an option", despite continued opposition to the Games in Japan, where vaccination rates are low and the number of positive cases continues to increase.
Bach, who undertook three days of quarantine upon his arrival in Tokyo two weeks ago and subsequently received a lukewarm reception on a visit to Hiroshima, was speaking at the start of the 138th IOC Session in the Japanese capital.
Bach said: "Cancellation would have been the easy way for us. We could have drawn on the insurance that we had at the time and moved on to Paris 2024.
"But in fact, cancellation was never an option for us - the IOC never abandons the athletes.
"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, it would have poured fuel on to this fire.
"Our doubts could have become a self-fulfilling prophecy. The Olympic Games could have fallen to pieces. That is why we had to keep these doubts to ourselves."
Latest figures indicate that over 70 Games-related personnel have tested positive for coronavirus since 1 July, including three athletes inside the Olympic Village.
Meanwhile, frustration has continued to mount over inconsistent quarantine measures for close contacts of a positive case, with athletes allowed to train and compete after a single negative PCR test, while others, including the Japanese public, must endure 14 days in isolation.
The Tokyo Games are the first to operate under a city-wide state of emergency, which has led to the Japanese government banning spectators from attending any Olympic events in the capital.
Friday's opening ceremony will also take place behind closed doors and is expected to be a dramatically scaled-back affair, with only media and dignitaries present, but it has been confirmed that Japan's Emperor Naruhito will attend.