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.

Despite the growing crisis, the Tokyo Olympics are still scheduled to go ahead on 23 July after having been postponed from last year.

Public opinion in the country has seen a vast majority of people calling for the Games to be cancelled though, or postponed a second time. The International Olympic Committee (IOC) has ruled out both those options.

A lot of people in Japan will be hoping that the CDC warning for Americans not to travel to Japan is a precursor to the US Olympic Team pulling out of the Tokyo Olympics.

Why? Because most people in Japan want the Games cancelled, and a US team withdrawal would almost certainly force the Japanese government to pull the plug.

For weeks people here have been saying Japan won't cancel without some outside pressure. There's even a name for this in Japanese - it's called "gaiatsu".

Those people look set to be disappointed. The US Olympic Committee says it is not changing its plans. Nor is the International Olympic Committee.

Last Friday IOC vice president John Coates said the Olympics will go ahead "even if Tokyo is still under a state of emergency".

That statement did not make him many friends in Japan, where daily deaths from Covid are now higher than at any time during the pandemic, and where the healthcare system in parts of western Japan has been described as "on the verge of collapse".

The United States Olympic & Paralympic Committee (USOPC) said the travel warning saying it would not affect their participation.

"We feel confident that the current mitigation practices in place for athletes and staff by both the USOPC and the Tokyo Organising Committee, coupled with the testing before travel, on arrival in Japan, and during Games time, will allow for safe participation of Team USA athletes this summer," it said in a statement.

Japanese officials on Tuesday responded to the US travel advisory, saying they did not expect it to have any impact.