U.S.A. Gymnastics on Monday also joined the calls for a postponement, following similar stances by national leaders in swimming and track and field. The three sports typically combine to deliver the most medals for the United States each Summer Olympics.

Li Li Leung, the chief executive of U.S.A. Gymnastics, said her federation’s decision was based on an anonymous survey of its athletes, in which nearly two-thirds of respondents said they favored delaying the Games for at least three months.

“It was really important for us to make sure our athletes’ voices were heard in this,” Leung told reporters during a conference call, adding that the athletes wanted to compete fairly without posing a health risk to others.

The I.O.C. and Tokyo need their decision to come in a way that resolves billions of dollars in financial implications.

“The bottom line is if the I.O.C. or Tokyo unilaterally decide to cancel or postpone without agreement, they would be in breach of contract and the potential financial repercussions are just enormous,” said John Mehrzad, a British sports lawyer who has represented national and international sports federations and athletes in litigation.

“As every day goes by and they don’t make a decision and other countries pull athletes out and the result of that means they can’t go ahead, then both parties will be delighted because it wouldn’t be their fault,” Mehrzad said. “If people try to sue them, they can blame factors out of control for why it isn’t taking place.”

A firm decision may come soon enough; Richard W. Pound, an I.O.C. member, said Monday that the Games would clearly not start as scheduled.