It will be difficult for Tokyo to host the Olympic Games next year unless there is an effective vaccine against the new coronavirus that causes COVID-19, the head of the Japan Medical Association (JMA) said Tuesday.

"I am not saying that Japan should or shouldn't host the Olympics, but that it would be difficult to do so," said JMA president Yoshitake Yokokura in a media briefing.

Yokokura also called on the nation to increase virus testing, which he said was not widespread enough to judge whether infection rates were falling. He also blamed a lack of gowns and other protective clothing for spreading the virus in hospitals.

The one-year delay of the 2020 Olympic Games announced last month was a major blow to Japan, which had already spent $13 billion preparing for the event.

With the outbreak having spread around the world, infecting almost three million people and killing more than 200,000, experts have warned that the fight against the virus could be prolonged.

Laboratories in several countries are working on vaccines to protect people against the virus and drugs to treat its symptoms. The need to conduct exhaustive clinical trials to test their effectiveness and safety, however, mean it could be months before they are widely available.