Japan's prime minister has pledged to do his utmost to prevent a resurgence of coronavirus ahead of the Olympic torch relay and his upcoming visit to Washington.

Yoshihide Suga was addressing his ruling Liberal Democratic Party's annual convention, just hours ahead of the planned lifting of a virus state of emergency in the the Tokyo region.

Mr Suga said the next period will be "an extremely important time" for virus prevention.

"We must not put our guards down... to prevent the infections from rebounding," he said.

Mr Suga on Thursday announced that the months-long emergency measures for Tokyo, Kanagawa, Chiba and Saitama would end at midnight on Sunday, a move underscoring his government's eagerness to minimise burdens on businesses and keep the economy going, despite concerns raised by experts about the potential for an upsurge.

The lifting of the measure comes just days before the Olympic torch relay starts from Fukushima, north-east of Tokyo and the site of the 2011 nuclear crisis, as a symbol of reconstruction.

Mr Suga renewed his pledge to achieve the Olympics in July as "proof of the victory against the coronavirus," after its one-year postponement due to the pandemic. Olympic officials decided on Saturday to bar spectators from abroad.

Mr Suga also wants to keep the infections low ahead of his planned Washington visit in early April for his first in-person summit with US president Joe Biden. He will be the first foreign leader to meet Mr Biden in person, underscoring the importance of the Japan-US alliance.

Mr Suga, who received the first shot of a Covid-19 vaccine last week, said he looks forward to discussing pandemic measures, as well as co-operation in dealing with China's growing influence in the region.

"We would still face ups and downs, but we will surely find a light ahead of us," Mr Suga said.

Mr Suga vowed to do the utmost to protect people's lives and health and sought their co-operation in doing what they can to get infections under control.

The measures have been in place for the Tokyo region since January 7 after daily infections surged to new highs in the area. The non-binding measures relied on requests for restaurants and bars to close at 8pm and take preventive measures.

The government will step up virus tests, monitoring for more contagious new variants and pay subsidies for restaurants and bars who co-operate to close at 9pm.

Experts have said they worry about the potential for a resurgence of infections now that the decrease in infections in the Tokyo area has levelled off and people grow fatigued with taking virus prevention measures.