TOKYO -- Secretary-General of Japan's ruling Liberal Democratic Party (LDP) Toshihiro Nikai said Thursday that cancelling the Tokyo Olympics this summer could be an option if the COVID-19 situation continues to worsen.

Nikai, the No 2 leader of Prime Minister Yoshihide Suga's ruling party, said in a TV show yet to be aired that cancelling the Games may be an option if the spread of coronavirus infections forces organizers to think it would be difficult to hold the event, according to Kyodo News.

His remarks came as the capital on Wednesday began a 100-day countdown until the beginning of the already postponed quadrennial event, with concerns rife that COVID-19 cases in and outside of Tokyo could be set to worsen.

Such is the severity of Japan's rebounding COVID-19 infections that the head of the government's COVID-19 panel warned that Japan has entered a "fourth wave" of infections.

Shigeru Omi, an expert in infectious diseases who heads the government's COVID-19 subcommittee, told a parliamentary session the previous day the central government should broaden the areas currently subjected to stricter antiviral measures under a revised law.

Omi said the expansion should be undertaken by the government "in an extremely swift and nimble manner."

On Monday, Tokyo, Kyoto and Okinawa prefectures were added to a list of regions where tougher virus measures have come into effect under a new law that falls short although is on the brink of declaring a state of emergency.