The State Department is warning Americans not to travel to Tokyo ahead of the Olympics

• Japan this year has experienced a sharp increase in COVID-19 cases.
• The surge has prompted calls to cancel or postpone the Tokyo Olympics.
• The US State Department just advised citizens not to travel to Japan.

The US State Department is warning Americans to not travel to Japan because of a rise in COVID-19 cases.

Two months ahead of the Olympics, the department on Monday issued a "Level 4: Do Not Travel" advisory, the highest warning against travel.

There have been mounting calls inside Japan to cancel or postpone the Olympics - where spectators from abroad were already barred - amid the country's coronavirus outbreak.

An online petition to cancel the Olympics, which went live last Wednesday, has garnered more than 388,000 signatures.

The billionaire SoftBank founder Masayoshi Son also joined the calls to at least delay the event, which is scheduled to begin July 23.

"Currently more than 80% of people want the Olympics to be postponed or canceled. Who and on what authority is it being forced through?" Son wrote on Twitter on Saturday.

A state of emergency in Tokyo has been extended until the end of May to try to contain the spread of the virus, as only 3.5% of the population has been vaccinated so far.

Japan has recorded more than 722,600 coronavirus cases, with more than 12,300 deaths, according to data from Johns Hopkins University.