'There is a risk the movement of people and opportunities to interact during the Olympics will spread infections and strain the medical system.'
Japanese medical experts warned on Friday that holding the Olympics during the COVID-19 pandemic could increase infections and said banning spectators was the least risky option, setting the stage for a possible face-off with organisers.
The experts, led by top health adviser Shigeru Omi, issued their warning in a report released after Tokyo 2020's organising committee chief told the Sankei newspaper she wanted to allow up to 10,000 spectators into stadiums for the Games, which begin on July 23.
Japan is pushing ahead with the multi-billion-dollar Games, postponed last year as the coronavirus was spreading around the world, despite opposition from the public, worried about another surge in infections.
Organisers have banned spectators from overseas but have yet to decide on domestic ones.
Cancellation of the Games - originally intended to showcase Japan's recovery from a devastating earthquake and nuclear crisis a decade ago - would be costly for organisers, the Tokyo government, sponsors and insurers.
"This event is different from ordinary sports events in scale and social interest and because it overlaps with summer vacations," the experts said in their report.
"There is a risk the movement of people and opportunities to interact during the Olympics will spread infections and strain the medical system."
They said that holding the Games without spectators is the "least risky" option and desirable.
The final decision will be taken at a meeting as early as Monday between organisers, including Tokyo 2020 and the International Olympic Committee, and representatives from the national and Tokyo governments.
Tokyo 2020 head Seiko Hashimoto told the Sankei newspaper in an interview published on Thursday she wanted the Games to be with spectators, and would head into the meeting with that in mind.
The advice from Omi would inform talks with the IOC and others, she said.
In a sign preparations are moving ahead, athletes from Uganda were due to arrive on Saturday, Kyodo news reported.
Prime Minister Yoshihide Suga's government decided on Thursday to end emergency coronavirus curbs in nine prefectures including Tokyo while keeping some "quasi-emergency" restrictions.
While Omi said no spectators is the most desirable option, his experts have floated the possibility that events could have up to 10,000 fans, but only in areas where the "quasi-emergency" measures, such as shorter restaurant hours, have been lifted.
Tokyo is scheduled to be under such restrictions until July 11. The current state of emergency, the third since April last year, expires on June 20.
The lifting of previous emergencies has been followed by increased infections and strains on hospitals.
Organisers should be prepared to act swiftly to ban spectators or declare another state of emergency if needed, the experts said. If spectators are allowed, rules should be strict, such as limiting fans to local residents, the experts said.
Omi, a former World Health Organisation official, has become increasingly outspoken about the risks from the event. He told parliament this month it is "not normal" to hold the Games during a pandemic.
Other Japanese health experts and medical organisation have been much more vocal, calling for the Games to be cancelled outright.
The public remains worried. Some 41% of people want the Games cancelled, according to a Jiji news poll released on Friday. If the Games go ahead, 64% of the public want them without spectators, the poll found.
One of the signatories of Omi's recommendations, Kyoto University professor Hiroshi Nishiura, said he believed cancelling the Games would be best, but the decision is for the government and organisers.
"If the epidemic situation worsened, no spectators and cancelling the Games in the middle (of the event) should be debated," he said.
Japan has not experienced the explosive COVID-19 outbreaks seen elsewhere but a recent surge and an initially slow vaccinations rollout prompted concerns about strains on the medical system.
The country has recorded more than 776,000 cases and over 14,200 deaths, while just 15% of its population has had at least one COVID-19 vaccination.