GENEVA — The head of the World Health Organization said Saturday it will not be easy to make next year’s Tokyo Olympics a safe global gathering after the pandemic.

Speaking at a joint news conference with the IOC, the WHO’s director general Tedros Adhanom Ghebreyesus called for “national unity and global solidarity” to fight the coronavirus outbreak ahead of the Olympics. The Games, postponed this year, should bring athletes from more than 200 countries to Japan.

The Summer Games opening ceremony is now due on July 23, 2021, after the International Olympic Committee and organizers in Japan used WHO advice in March before agreeing a one-year delay.

“We hope Tokyo will be a place where humanity will gather with triumph against COVID,” Tedros said at WHO headquarters.

“It is in our hands, but it is not easy. If we do our best, especially with national unity and global solidarity, I think it’s possible,” he said.

Around 11,000 athletes from more than 200 teams are due to compete at the Tokyo Olympics. Most would be joined by team officials staying in an athletes village complex of 5,600 apartments at Tokyo Bay.

Health experts, including in Japan, have questioned how the 33-sport Olympics can be run before an effective global vaccine program is in place.

“Nobody can at this moment in time really give you a reliable answer on how the world will look like in July 2021,” IOC President Thomas Bach acknowledged.

“It is too early to start speculation on different scenarios and what it may need at the time to guarantee this safe environment for all participants.”

Tedros and Bach signed a renewed working agreement between the two organizations, which aims to help promote sport to governments as part of an active and healthy lifestyle.

“The Olympics or athletics or football is not just for the athletes only,” Tedros said. “It has to be a culture for everybody and it has to be everybody’s responsibility.”