At a press conference on Monday, he said restaurants and drinking establishments should be asked to shorten their opening hours. He pointed out that footfall in nightlife districts did not drop by much in December. "The details will be worked out quickly to effectively reduce the risk of people getting infected while dining out," he said.
Government officials say the state of emergency could be in place for Tokyo and the three neighboring prefectures as early as this week.
The prime minister is able to make the declaration thanks to a special anti-coronavirus law. Suga will also need to specify a duration.
Under a state of emergency, prefectural governors can ask residents to refrain from all but essential outings. Governors can also ask or instruct schools, department stores and other facilities that draw crowds to close or limit operations.
Sources say leaders in Tokyo and the other three prefectures are considering asking restaurants to bring their closing times forward to 8 p.m., and asking residents to refrain from making non-essential outings after 8 p.m. from this Friday to the end of this month.
A state of emergency was declared in Tokyo and six other prefectures on April 7 last year. It was later expanded to cover the whole country.
Currently, there are no penalties for failing to comply with any measures set out. However, Suga says the government will attempt to change that by proposing a legal revision this month.
Japan is battling a so-called "third wave" of coronavirus infections. Tokyo reported 1,337 new cases on December 31. It was the first time the daily tally exceeded 1,000.
On Saturday, Tokyo Governor Koike Yuriko and her counterparts in Chiba, Saitama and Kanagawa petitioned the central government to declare a state of emergency.
Koike vowed to take action quickly, saying, “Tokyo and the three prefectures will work as one to effectively implement measures for transportation, working from home and flexi time.”
Suga said the central government aims to start vaccinating medical professionals, seniors and care home workers by late February.
He also said he still hopes Tokyo will host the Olympics and Paralympics later this year. He said the Games, which were postponed last year due to the pandemic, will be an opportunity to show that humankind has overcome the pandemic.