Japan's medical system is struggling to cope with Covid-19
The US has issued a travel warning for Japan over the country's Covid-19 surge, amid heightened scrutiny just weeks before the Tokyo Olympics.
But US Olympic officials have said they are confident their athletes will be able to take part safely in the Games.
Japan already bans most travellers from entering the country.
It long had low numbers of Covid cases but is now seeing a fresh wave of infections pushing the healthcare system in some cities to its limit.
Japan has recorded more than 700,000 infections and 12,000 Covid-19 deaths from the virus.
The US Center for Disease Control (CDC) said "travellers should avoid all travel" to the country, warning that in the "current situation in Japan even fully vaccinated travellers may be at risk for getting and spreading" Covid variants.
Largely due to the global pandemic, the US currently has 151 countries at level four, its highest alert level, including most of Europe where large sports events go ahead under special Covid restrictions.
Japan currently does not allow any tourists or business travellers into the country for fear of new strains of the virus. The Japanese ban includes people coming from the US being "denied permission... unless there are exceptional circumstances".
Large parts of the country are currently under a state of emergency to give regional authorities more power to enforce measures against the pandemic.