TOKYO -- Japan is set to expand a state of emergency to eight more prefectures, taking the total to 21, the minister in charge of coronavirus countermeasures said on Wednesday, as a surge in COVID-19 cases overwhelms its hospitals.

Economy Minister Yasutoshi Nishimura said the expansion, which would cover almost half the country's 47 prefectures, was approved by a panel of external experts. It is expected to be formally approved at a government task force meeting later on Wednesday.

"The most important task is to beef up the medical system," Nishimura said, adding that securing oxygen stations and nurses was among the priorities.

With the Delta variant spreading fast, the government has struggled to bring infections under control as citizens grow weary of life under restrictions and many companies ignore repeated requests to promote work-from-home.

Public broadcaster NHK reported21,570 new cases and 42 deaths on Tuesday. Japan's case fatality rate stands at about 1.2%, compared with 1.7% in the United States and 2.0% in Britain.

Months of emergency curbs in the capital, Tokyo, and surrounding areas have failed to reverse a surge in infections and about 90% of the city's critical care beds are occupied.

"The working-age demographic is the driving force (behind the rise in infections)," Nishimura said. "We need to halve the movement of people."

With hospital beds filled to or nearing capacity, many people have been forced to convalesce at home - some dying before they are able to get treatment.

The latest state-of-emergency expansion will add Hokkaido, Aichi, Hiroshima and five other prefectures spanning the Japanese archipelago from Friday through Sept. 12.

Another four prefectures are expected to be added to the more limited "quasi-emergency" measures, bringing the regions under those curbs to a total of 12.

Restrictions in Japan have been looser than lockdowns seen in some countries and have centred on mandates for restaurants to close by 8 p.m. and stop serving alcohol, and requests for companies to have 70% of staff working from home.