The head of a Japanese physicians’ group said that it would be "exceedingly difficult" for Japan to host the Tokyo Olympics in the summer of 2021 unless a COVID-19 vaccine is available.

The plan of delaying the Games until July 23, 2021 would require an improved “global situation,” Dr. Yoshitake Yokokura, the president of the Japan Medical Association, told reporters on Tuesday. “My personal opinion is that if an effective vaccine has not been developed it will be difficult to hold the Olympic Games,” he said.

“I would not say they should not be held, but I would say that it would be exceedingly difficult,” Dr. Yokokura added.

On Tuesday, Yoshiro Mori, the president of the Tokyo 2020 organizing committee, was quoted as telling a Japanese newspaper that the Games would be “scrapped” if they could not take place next July.

“The Olympics would be much more valuable than any Olympics in the past if we could go ahead with it after winning this battle,” Mr. Mori told the Nikkan Sports daily. “We have to believe this. Otherwise our hard work and efforts will not be rewarded.”