Postponing the Tokyo Olympics would be unavoidable if they can not be held in a complete way because of the coronavirus, Japan's prime minister Shinzo Abe said on Monday.
But Abe ruled out cancelling the Games altogether.
His comments in the Japanese parliament came after the International Olympic Committee (IOC) said it would make a decision on a postponement within four weeks.
They also came as Canada said it would not send athletes to the Games unless they were postponed by 12 months, as Australia told its athletes to prepare for an Olympics next year, and as British officials urged the IOC to make a decision soon.
In a statement, the Canadian Olympic Committee (COC) and the country's paralympic committee "urgently" called on the IOC, the International Paralympic Committee (IPC) and the World Health Organisation (WHO) to postpone the Games for one year.
"We offer them our full support in helping navigate all the complexities that rescheduling the Games will bring," the statement said.
"While we recognise the inherent complexities around a postponement, nothing is more important than the health and safety of our athletes and the world community."
The Australian Olympic Committee said in a statement: "Australian athletes should prepare for a Tokyo Olympic Games in the northern summer of 2021."
It added the Australian team "could not be assembled in the changing circumstances at home and abroad".
Abe told parliament postponing the Games - due to start on July 24 - may be an option if holding the event in "complete form" became impossible.
"If it is difficult to hold (the Games) in a complete way a decision of postponement would be unavoidable as we think the athletes' safety is paramount," he said.
The Olympics have never been postponed or cancelled during peacetime.
Like Abe, the IOC has continued to insist "cancellation is not on the agenda".
But in response to growing calls for a delay over the Covid-19 pandemic, the IOC now accepts the Games could be moved to a new date.
The IOC's executive board said it would now step up its "scenario-planning" to look at the different possibilities in what is an ever-changing situation in Japan and globally.
A statement read: "The IOC will, in full coordination and partnership with the Tokyo 2020 organising committee, the Japanese authorities and the Tokyo metropolitan government, start detailed discussions to complete its assessment of the rapid development of the worldwide health situation and its impact on the Olympic Games, including the scenario of postponement."