Spectators will be allowed to line the route when the Olympic flame begins its delayed relay across Japan next month, organisers said Thursday, but cheering will be strictly banned.

The torch relay was scrapped just days before it was due to kick off last year when Japanese and Olympic officials took the unprecedented decision to postpone Tokyo 2020 over the coronavirus pandemic.

Despite persistent concerns about the safety of holding the Games this summer, organisers say the massive event can go ahead and the torch relay will kick off as planned on March 25.

"The infection situation will vary from area to area, so we need to take that into account and it will be very important to have a meticulous approach," Tokyo 2020 president Seiko Hashimoto told reporters.

"We want to get the understanding of people in every area and connect the whole country under the torch relay concept 'Hope Lights Our Way'."

Hashimoto later said she hopes a decision on how many fans are allowed into Olympic arenas will be taken around the time the torch relay begins. Organisers had previously said it would be taken "in spring".

"I think we need to have an indication of which way things are going around the time the torch relay starts," local media quoted her as saying.

The torch relay will start from a symbolic site in Fukushima, highlighting the role of Tokyo 2020 in what Japan has dubbed the "Reconstruction Olympics" -- after the 2011 earthquake, tsunami and nuclear disaster.

But the relay will be a much more sober affair than usual.

Spectators will be allowed to watch the flame pass, but will be required to wear masks, avoid crowding, and only attend segments of the relay near their home.

"They must support with applause or by using distributed goods rather than by shouting or cheering," guidelines warn, adding social distance must be maintained.

"Individual relay segments will be suspended if there is a risk of overcrowding," the guidelines add.

Attendance at celebration venues along portions of the route will be by reservation only to limit numbers.

And information on which torchbearers will run which sections will be released only at the last minute to avoid crowds gathering to watch celebrity runners.

Very difficult' to have foreign runners

"We're not trying to discourage people from coming out to watch," said Tokyo 2020's torch relay office executive director Teruhiko Okada. "The most important thing is to avoid having crowded areas."

Torchbearers will be able to run without masks -- news likely to be welcomed by those running in the later stages when Japan's fierce summer heat has kicked in.

Both runners and staff will have to keep detailed health records in the two weeks before their participation, and avoid risky activities -- including eating out or going to crowded places.

But organisers say the relay will not be automatically stopped if a runner who has taken part later tests positive, and that the "basic policy" is to continue unless there is a large-scale cluster.

Around 300 runners from outside Japan were set to take part last year -- but organisers said it would now be "very difficult" for them to join in. Japan's borders are closed to almost all foreign arrivals as part of the country's virus control measures.

Parts of Japan are currently under a virus state of emergency due to lift by March 7, with some areas possibly exiting the measure earlier.

The guidelines warn that segments of the relay could be suspended if the measure is reimposed in areas where the torch relay will take place.

The relay is set to visit each of Japan's 47 prefectures, but there is some opposition.

Tatsuya Maruyama, governor of sparsely populated Shimane Prefecture in western Japan, has warned he may cancel events if the virus situation does not improve, and met with government officials in Tokyo to repeat his concerns, reports said.

The Games are scheduled to open on July 23, and organisers have outlined virus guidelines they say will allow the event to be held safely.

Final decisions on some key elements remain, with IOC chief Thomas Bach saying yesterday a ruling on whether to allow foreign spectators could come in April or May.