International Olympic Committee President Thomas Bach said the rescheduled Tokyo 2020 Games would have to be canceled if it cannot take place next summer.
Earlier, the IOC and Japanese government took the unprecedented decision to delay the Tokyo Games, which had been due to start in July, for a year due to the novel coronavirus outbreak.
Japanese Prime Minister Shinzo Abe said the multi-sports event cannot take place in 2021 unless the virus is contained and Bach said he understood his position.
"You cannot forever employ 3,000 to 5,000 people in an organizing committee," Bach told BBC Sport. "You cannot have the athletes being in uncertainty."
The coronavirus has infected more than 17,100 people in Japan, causing 797 deaths.
Bach said the IOC has different scenarios under consideration and it isn't easy to address them now.
"What could this mean for the life in an Olympic Village?" he said.
"All these different scenarios are under consideration and this is why I'm saying it's a mammoth task, because there are so many different options that it's not easy to address them (now)."
Bach said re-organizing the Games will be a mammoth task.
He warned that the event would definitely be different with a focus on essentials.
Bach said staging the Games behind closed doors was not what the IOC wants.
However, he needs more time to consider whether that was feasible.
He didn't want to be drawn on whether vaccination would be needed for the event.
Japan's PM Shinzo Abe has admitted it may be "difficult" to stage the Tokyo Olympics if the country does not successfully contain the virus.
The head of the Japan Medical Association has suggested it depends on finding a vaccine.
When asked about his views to these claims, Bach said, "For this question, we are relying on the advice of the World Health Organization."
"We have established one principle: to organize these Games in a safe environment for all the participants. Nobody knows what the world will look like in one year, in two months."
"So we have to rely on [experts] and then take the appropriate decision at the appropriate time based on this advice," Bach told BBC Sport.
The Euro 2020 was postponed to 2021 after European football's governing body took the decision in March.
In tennis, the Wimbledon 2020 event was scrapped altogether.
Meanwhile, the French Open, which was supposed to be held between May 24 to June 7, will now commence on September 20.
In cricket, the ICC T20 World Cup could get postponed to next year.
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