Tokyo 2020 organisers have started drafting possible alternatives to holding the Olympics in July-August, in contrast to the Japanese government's stance that postponement is not an option.
While the coronavirus outbreak has disrupted sports events around the world, Japan has been steadfast in saying the Games will go on as planned.
Prime Minister Shinzo Abe has staked his legacy as Japan's longest-serving premier on the Games and is hoping for a boom in tourism and consumer spending. At risk is more than $US3 billion ($A5.2 billion) in domestic sponsorship, an Olympic record, and some $US12 billion ($A21 billion) spent on preparations.
"Finally, we have been asked to make a simulation in case of a postponement," said a Reuters source, an official close to the organising committee and involved in drafting the scenarios.
"We are making alternative plans - plan B, C, D - looking at different postponement timeframes," said the official, adding the scenarios included cost estimates for different delays.
The options, which included scaling back the Games or holding them without spectators, would be debated by the organising committee at the end of March, the official said.
A second source, also close to the Tokyo 2020 organising committee, confirmed that postponement was being discussed, including delays of one or two years.
Some organising staff were holding out hope for a delay of a month or 45 days, said the official involved in drafting the scenarios.
A final decision on postponement will have to come from the IOC but Japan's stance also matters.
The IOC and its powerful chief, Thomas Bach, have stated the Games will go ahead as planned, drawing fire from athletes who say that represents a health risk.
Two other insiders, both senior members of the Tokyo 2020 organising committee, echoed those concerns. One of them, a committee board member, said the decision to postpone should be made quickly.
"The more they push the decision away ... more and more preparations have to be made - this will cause cancellation fees to go through the roof," the board member said.
The official involved in drafting scenarios said a long delay might spark complaints from older athletes and require keeping sponsors on board for longer. Another headache is the Olympic village, due to be converted to flats after the Games.
The summer 2021 calendar is already crowded while 2022 features the soccer World Cup and the Beijing Winter Olympics.
Japanese sponsors are nervous, company representatives have said privately. Major sponsors include Toyota Motor Corp and Panasonic Corp.
"Of course, companies are individually discussing what to do," said a representative of one of the more than 60 sponsors. "No one wants to be the first to say anything about the possibility of a postponement."
Japan Airlines Co discussed that there was an 80 per cent chance the Olympics would not be held as scheduled on a recent internal conference call, a person briefed on the call said.
A JAL spokesman said: "Our preparations are under way for the Games to open as scheduled".
In Tokyo, there is a sense delay might be inevitable. Finance Minister Taro Aso has compared Tokyo 2020 to the 1940 Olympics cancelled by World War II, and the boycott of the 1980 Moscow Games.
"It's a problem that's happened every 40 years," he said. "It's the cursed Olympics - and that's a fact."