The coronavirus pandemic prompted Australia to withdraw athletes from the 2020 Olympics on Monday.
With athletes unable to train or prepare properly due to social distancing and a clampdown on travel, the Australian Olympic Committee (AOC) joined Canada and announced it could no longer assemble a team for the July 24-August 9 Games in Tokyo.
"It’s clear the Games can’t be held in July," Australia Chef de Mission Ian Chesterman said on Monday, three days after telling reporters the team was committed to the schedule.
"Our athletes have been magnificent in their positive attitude to training and preparing, but the stress and uncertainty has been extremely challenging for them."
Australia had previously been in lock-step with the International Olympic Committee (IOC), which until Sunday had insisted the Games would go ahead as scheduled.
After weeks of pressure, the IOC finally said postponement was in its "scenario planning", with a decision expected in four weeks.
The timeframe was not quick enough for the AOC, however, which announced its decision shortly after Canada became the first country to boycott the Games.
AOC Chief Executive Matt Carroll said he hoped the Games would go ahead in Tokyo, but not until the summer of 2021.
"We've had to make a call now because of the situation here in Australia and other parts of the world," Carroll said in Sydney.
Australia's Paralympic committee and sports federations backed the AOC's stance. Swimming Australia (SA) said it was "devastating" for athletes but the correct decision.
"Given the current situation worldwide, it has become evident that it is not safe for the Games to be staged in its current time frame,” SA Chief Executive Leigh Russell said.
Australians began living under strict new lockdown rules on Monday as coronavirus cases topped 1,600.
Australia's National Rugby League suspended its season indefinitely after only two rounds of the championship.