Canada has become the first country to boycott the Tokyo Games due to the coronavirus pandemic and Australia told its athletes to prepare for an Olympics next year as Japan and the IOC flagged the prospect of a postponement for the first time.
Opposition to holding the Games in July rose sharply at the weekend when major stakeholders such as US Track and Field and UK Athletics, along with some national Olympic committees, called for a delay because of the pandemic.
Canada's Olympic and Paralympic Committees raised the ante considerably, however, when they said they would not send athletes to Tokyo if the Games went ahead as scheduled.
Britain wants the IOC to make a "definitive decision" soon on whether the summer Olympics should go ahead, Prime Minister Boris Johnson's spokesman said on Monday.
Under mounting pressure to postpone the Games, the International Olympic Committee (IOC) and Japanese government had on Sunday and Monday had only partially shifted their position that the Games would go ahead as planned.
Martin Richard, communications chief for the Canadian Paralympic Committee, said the Canadians had been watching for a decision from the IOC on Sunday about postponing the Games and decided to withdraw when none came.
On Sunday, the IOC said it would hold discussions during the next four weeks that would include an option of putting back the July 24 start date or even moving the Games by a year or more.
Japanese Prime Minister Shinzo Abe told parliament on Monday that postponing the Olympics may become an option if holding the Games in its "complete form" became impossible.
Abe also said calling off the Games entirely "was not on the agenda".
Tokyo 2020 Olympics chief Yoshiro Mori later said organisers would consider postponement as one of many scenarios they aim to have ready in the next four weeks.
And the country's Olympics organising committee announced on Monday plans to dramatically scale back the torch relay until a formal decision on the Games is made, public broadcaster NHK said on Monday.
The event, which was due to start on March 26 will be more of a "tour" than a relay, NHK said.
Soon after Canada's move, the Australian Olympic Committee released a statement saying it had told its athletes to prepare for a Tokyo Games taking place in 2021.
Canada's boycott will add to growing pressure on the IOC to alter the schedule after criticism from a slew of current and former athletes.
"YESSSSSS CANADA!!!!!!! pulls out of OLYMPICS UNLESS IOC POSTPONE!!!," tweeted US former Olympian Lolo Jones. "OUR HEALTH IS MORE important than sport. Hopefully the UNITED STATES is next."
The the US Olympic and Paralympic Committee said it would not comment on Sunday about Canada's decision.
But the Russian Olympic Committee (ROC) on Monday said the world's sporting authorities need to make balanced decisions based on logic and analysis in the face of coronavirus "panic" to determine whether Tokyo 2020 will go ahead this summer.
All members of the sporting community need to remain calm and act steadily and constructively to form a unified position, the ROC said in a statement on its website
The Olympics have never been postponed or cancelled during peacetime but the IOC's decision to even consider postponement was met with relief from several major stakeholders, including World Athletics, the International Paralympic Committee and major national Olympic committees.
The last major boycott of the Olympics was when the Soviet bloc stayed away from the 1984 Los Angeles Games, although North Korea and Cuba skipped the 1988 Seoul Olympics.