Tokyo 2020 President Seiko Hashimoto has acknowledged the Olympic and Paralympic Games may be held behind closed doors as organisers seek to ease concerns over hosting the multi-sport event.
Organisers announced earlier this week that a decision on spectator limits at the Games will not be taken until June.
The decision would come a month prior to the planned July 23 Opening Ceremony of the Olympic Games.
It had been due to be made by the end of this month - fans from overseas have already been banned - before the rise in coronavirus cases in Tokyo and several other areas forced a delay.
Hashimoto admitted on Wednesday (April 28) that full capacity would be "very difficult" and today acknowledged fans might be prohibited from the Games.
"There might be a situation where we can't allow any spectators to attend," Hashimoto told Agence France-Presse.
"The only way that we can call the Games a success is if we completely protect the lives and health of athletes and the people of Japan."
"If the event itself does change, I think it will be with regard to spectators.
"That is one area where we might be able to reduce the anxiety of people who are worried about the medical system."
Tokyo 2020 held an expert roundtable today regarding COVID-19 countermeasures, with organisers claiming they are still planning for the possible attendance of domestic fans at the Games.
The roundtable followed this week's publication of the second version of the playbook for athletes and officials at the Games by Tokyo 2020, the International Olympic Committee (IOC) and International Paralympic Committee (IPC).
The playbooks confirmed there will be daily saliva testing for athletes and all those with close proximity to competitors, while all participants at the Games will be required to take two COVID-19 tests within 96 hours before they fly to Japan.
Officials, coaches and the media will be tested daily for three days after their arrival in the host country.
Participants will also only be able to eat in designated areas, such as their hotel restaurant, venues and their room, during the entirety of the Games.
All those attending the Games will have to fill out a mandatory written pledge confirming they will adhere to the rules in the playbook, along with proof of a negative test, before they are allowed into Japan.
Those who fail to comply with the measures could be stripped of their accreditation.
Tomoya Saito, director of the Centre for Emergency Preparedness and Response (CEPR) at Japan’s National Institute of Infectious Diseases, said he had raised the issued of punishments at the roundtable.
“We want to entice people to follow the rules and one way of doing that is ensuring the countermeasures are doable, easy to do and make them want to do it," Saito said.
"On the other hand, the second way is to come up with penalties and sanctions.
"We have to have fair judgements, so we need a third-party point of view.
"We want to have as positive a take on these Games as possible and want people to feel natural about following these rules and complying.
"We want to nurture a collective awareness and understanding to follow the rules to have a fun Games."
Tokyo 2020 Games delivery officer Hidemasa Nakamura said some form of sanctions would need to be in place at the Games.
Nakamura said organisers wanted to produce "reasonable and fair" sanctions, as well as understanding how the punishment process would operate.
The Tokyo 2020 official acknowledged that this may prove easier with athletes, as they will reside in the Athletes’ Village.
Nakamura said organisers would have to consider how to ensure the rules were "practical" and enforceable for stakeholders who will be staying outside the Athletes’ Village during the Games.
Tokyo is among the prefectures under emergency measures to curb the spike in COVID-19 infections introduced around the country's Golden Week holidays, which began yesterday.
Public opposition to the Olympic Games, scheduled to open on July 23, remains high in Japan because of the global health crisis.