This summer's virus-postponed Olympics could be held behind closed doors, Tokyo 2020 president Seiko Hashimoto said on Friday, pledging to ensure the Games will be safe. 

Former Olympian Hashimoto said the Games could only be a success if organizers "completely protect" athletes and people in Japan, and that she is hopeful people will "be glad" the event went ahead. 

Overseas spectators have already been barred from the Games, and this week a decision on domestic fans was delayed until June, with organizers citing a new wave of infections in Japan. 

"There might be a situation where we can't allow any spectators to attend," Hashimoto conceded in an interview with AFP. 

Most people in Japan back either a further delay of the Games or an outright cancellation, and a recent surge in virus cases has prompted a state of emergency in Tokyo and other parts of the country. 

With the medical system already under pressure, Olympic organizers have been criticized for requesting volunteer medical staff for the Games. 

Hashimoto said cutting spectators could ease pressure on the medical system. 

"That is one area where we might be able to reduce the anxiety of people who are worried about the medical system." 

The Games have never been cancelled outside of wartime and organizers have made it clear that they see no possibility of either further delay or a cancellation. 

In a bid to win public confidence, they have released "playbooks" mandating daily testing for athletes and limiting their movement. 

But there will be no quarantine required for athletes, and vaccines will not be mandatory. 

The recent spike in infections has played havoc with Olympic preparations, forcing changes to test events and qualifiers and prompting several regions to take the nationwide torch relay off public roads. 

Hashimoto said organizers accepted that the situation would continue to change, and that they were running simulations to adapt as necessary.