TOKYO — A week ago, Prime Minister Shinzo Abe of Japan and Thomas Bach, president of the International Olympic Committee, were promoting the Summer Olympics in Tokyo as the balm the world needed to show victory over the coronavirus pandemic.
On Tuesday, the virus won out.
Bach and Abe bowed to a groundswell of resistance — from athletes, from sports federations, from national Olympic committees, from health experts — and formally postponed the Games, which had been scheduled to begin in late July, until 2021.
The decision brought both a sense of relief and impending chaos to international sports.
Abe broke the news after a phone call with Bach, when complaints that the I.O.C. was not moving quickly enough to adjust to the coronavirus pandemic became too loud to ignore.
The decision — which organizers in Japan resisted the longest, according to people involved with the process — became all but inevitable after the national Olympic committee in Canada announced on Sunday that it was withdrawing from the Games, and Australia’s committee told its athletes that it was not possible to train under the widespread restrictions in place to control the virus. Brazil and Germany, too, called for postponing the Games. And the United States Olympic and Paralympic Committee, after initially declining to take a stand, joined the fray Monday night, urging the I.O.C. to postpone.
In announcing the decision, Abe said that he had asked Bach for a one-year delay and that Bach had “agreed 100 percent.”
It was an extraordinary turnabout: The Olympics have been canceled only because of world wars, in 1916, 1940 and 1944, and have carried on even in the tense climate after the terrorist attacks of Sept. 11, 2001, and at the 1972 Munich Olympics, where 17 people died after the quarters of the Israeli team were stormed by Palestinian terrorists.
Bach said the situation had become untenable in recent days as the World Health Organization described the acceleration of the virus in Africa to Olympic leaders. That forced the I.O.C. to shift its focus from whether Japan could be safe at the start of the Games to what was immediately happening in various other countries.
“We had growing confidence in the developments in Japan,” Bach said in a conference call with journalists. “In 4½ months, these safe conditions could be offered. Then we had this big wave coming from the rest of the world.”
As the virus spread, Bach said, athletes began voicing concerns about risking their health to continue training. It became clear that the pandemic was “rocking the nerves of the athletes, and it’s also not a situation we have ever been in,” he said.
Bach said that finalizing the details of a new schedule and negotiating adjustments in the global sports calendar with leaders of international federations, who were caught off guard by the speed of the decision, would take time.
“There are a lot of pieces of a huge and very difficult jigsaw puzzle,” he said.
Yoshiro Mori, the president of the Tokyo organizing committee, said that the scope and the dates of the Games in 2021 were uncertain, but that it was clear that they could not be held anytime in 2020.
“I am disappointed,” Mori said. “But to be on course with a certain direction is a sigh of relief.”
The postponement could result in adjusting the dates to avoid the hottest weeks of the summer in Tokyo, a concern Olympic organizers faced before the pandemic.
The I.O.C. considered other alternatives, like holding the Games without fans in arenas or delays of varying lengths — from just a few months to all the way to 2022. The committee’s leaders never seriously considered fully canceling the Games or taking them away from Tokyo, but executives with the local organizing committee were caught by surprise at how quickly things had changed from Sunday’s declaration by the I.O.C. that it would make a decision on rescheduling the Games within four weeks.
Bach had been emphasizing that life was returning to normal in Japan, which has not been hit as hard by the virus as China, Italy, Spain and the United States. On Sunday in Sendai, in Northern Japan, about 50,000 went to a welcoming ceremony to view the Olympic flame, and people in Tokyo have been taking the subways and dining in restaurants, a stark contrast to life in coronavirus hot spots closer to the I.O.C. headquarters in Switzerland.
“This call was arranged hastily,” said Toshiro Muto, chief executive of Tokyo 2020, the local organizing committee, referring to the conference call between Abe and Bach on Tuesday evening in Tokyo.
Abe started his day discussing the Olympics with Prime Minister Justin Trudeau of Canada. He finished with a hearing on the economic impact of the coronavirus, then returned to his official residence for his call with Mr. Bach. Shortly before the call, leaders of the Games in Tokyo, including Mori, the Tokyo governor, Yuriko Koike, and Seiko Hashimoto, Japan’s Olympics minister, arrived at the residence to join him.
Muto said the decision would cause countless complications. Thousands of tickets have been sold to people in Japan and abroad, who may no longer be able to use them. Japan has already invested at least $10 billion in the Games after beating out Madrid and Istanbul to win the rights to host, and the delay will undoubtedly increase costs. Leases on many of the competition venues and contracts with employees will have to be extended.
“When it comes to who is going to pay for it, that is what we are going to discuss going forward,” Muto said.
The decision quickly gained the support of national Olympic committees from around the world. In a statement, Andy Anson, the chief executive of the British Olympic Association, said a postponement was the only decision his organization could support. “It would have been unthinkable for us to continue to prepare for an Olympic Games at a time the nation, and the world no less, is enduring great hardship,” Anson said.
Sarah Hirshland, the chief executive of the United States Olympic and Paralympic Committee, which did not support a postponement until Monday night, said in a letter to Team U.S.A. athletes, who had become increasingly frustrated by her lack of action, that “taking a step back from competition to care for our communities and each other is the right thing to do.”
The signal that the decision was certain came earlier Monday, when Australia announced that it would not be able to send a team to Tokyo. John Coates, the leader of Australia’s Olympic organization and an I.O.C. member, is a close ally of Bach’s and leads the I.O.C.’s coordination commission for the Tokyo Games.
At a time when Japan’s economy is already stumbling, the delay of the Olympics could deal a serious blow. In a report early this month, SMBC Nikko Securities Inc. projected that a cancellation of the Games would erase 1.4 percent of Japan’s economic output.
One of the trickiest aspects of moving the Games is handling the broadcast rights that drive significant revenue for the International Olympic Committee. Nearly three-quarters of I.O.C. revenue comes from broadcast rights, and about half of those fees are paid by the American broadcaster NBC. Broadcast partners and other Olympic partners may seek a reduction in their fees if there are substantial changes to when the Olympics are staged or if organizers reduce the number of sports.
The complications will ripple beyond the Games themselves. The international governing bodies for track and field and swimming, for example, planned to hold world championships in 2021 and will have to work with their athletes and host cities to possibly reschedule those events.
The Summer Olympics attract more than 11,000 athletes from more than 200 countries, and the I.O.C. prides itself on being more than a competition, representing values such as unity and peace, bringing the world together every two years in sports and friendship.
The coronavirus initially broke out in China in December but has quickly spread across Asia, Europe and North America, and many health experts have been concerned that bringing together people from disparate parts of the globe — especially athletes who live closely in a village — might ignite an additional outbreak.
The Olympic torch relay through Japan was scheduled to start Thursday. The flame will now stay in Fukushima, site of the nuclear meltdown triggered by an earthquake and tsunami nine years ago.