Japan's Asahi Shimbun, an official partner of the Tokyo 2020 Olympics, called for the Summer Games to be cancelled in an editorial on Wednesday, citing risks to public safety and strains on the medical system from the COVID-19 pandemic.

Poll after poll has shown the majority of the public is opposed to holding the Games this summer, concerned about tens of thousands of athletes and officials descending on a country that has mostly remained closed to foreigners since last year and where vaccinations have proceeded slowly.

Doctors' associations have protested holding the Games, investors have talked up the benefits of shelving them, and maverick businessmen such as Masayoshi Son have called for cancelling the games.

That Asahi, one of Japan's most prestigious newspapers, broke ranks with other partners is likely to intensify focus on the viability of the Games.

"We ask Prime Minister (Yoshihide) Suga to calmly and objectively assess the situation and decide on the cancellation of the event this summer," said the paper, a left-leaning daily often critical of Suga's ruling Liberal Democratic Party.

"We are far from a situation in which everybody can be confident they will be 'safe and secure,'" the paper added, invoking the government mantra about the Games. "Sadly, that is not the reality."

Several of Japan's other major dailies, such as the Nikkei, the Mainichi and the Yomiuri, are also Tokyo 2020 official partners.

The Asahi's editorial was widely shared on social media, garnering more than 30,000 tweets by late morning.

Much of Japan, including host city Tokyo, remains under a third state of emergency that is widely expected to be extended beyond this month, and although Japan has been spared the coronavirus ravages of overseas nations, it has struggled to control a fourth wave of infections across the country.

Just over 5% of the nation has received vaccinations, and it has recorded about 719,000 infections and 12,394 deaths.

A professor of public health and adviser to the New Zealand government said on Tuesday that going ahead with the Games was "absurd".

The United States on Monday issued an advisory against travel to Japan, but Japanese officials said it would not affect the Games, and the White House said on Tuesday it stood by the decision to hold the Games as planned.

The Australian softball team is set to arrive in Japan on June 1 for a pre-Olympic training camp in Gunma, a prefecture about 150 km northwest of Tokyo.