The embattled centre-left leader has announced a full review of Japan's energy plan, under which atomic power had been set to meet over half of demand by 2030, up from about one third before the March 11 quake-tsunami disaster.
Kan, who started his political life as an environmental activist, has said he wants to make clean energy sources such as solar, wind and geothermal a new "major pillar" of the industrial power's energy mix.
The premier, Japan's fifth in as many years, is making the speech at a time when he is under intense pressure to step down from political adversaries who accuse him of having bungled Japan's response to the tsunami.
Kan has butted heads with plant operator Tokyo Electric Power Company (TEPCO) over the Fukushima Daiichi nuclear accident, the world's worst since Chernobyl 25 years ago.
The premier's skepticism about boosting nuclear power in the quake-prone island nation has also set him on a collision course with pro-nuclear lawmakers, both in the conservative opposition and within his own party.
The earthquake and tsunami crippled the Fukushima plant, which has suffered meltdowns and explosions and radiation leaks into the air, soil and sea.
With all but 19 of Japan's 54 reactors now shut, mostly for regular checks, Japan is going through a power crunch in the sweltering summer months, and there are fears that outages could slow the already limping economy.
"There are worries about power supply in Japan," said Economy Minister Kaoru Yosano on Wednesday. "Manufacturers may well consider moving plants to a country with a stable electricity supply or cheaper labour."
Kan, in a press conference scheduled for 6:00pm (0900 GMT), was expected to present what he terms a "realistic" plan to ease the nation's reliance on nuclear power, the Nikkei financial daily and other media reported.
Speaking in parliament on Tuesday, Kan said: "We should start over from scratch... We can't help but lower our reliance on nuclear."
He also suggested that nuclear power companies may need to be nationalised, calling for debate about the ability of the private sector to run atomic power plants, given TEPCO's multi-billion-dollar compensation bill.
Anti-nuclear sentiment in Japan has grown since the Fukushima disaster, and thousands have since protested at a string of rallies against TEPCO and nuclear power and for a shift toward alternative energy.
Telecom giant Softbank has announced plans to build 10 large-scale solar power plants. Its president Masayoshi Son and 36 of Japan's 47 prefectures launched a council Wednesday aimed at boosting renewables.
The liberal, mass-circulation Asahi Shimbun daily Wednesday called for a shift toward a nuclear-free society within two or three decades.
It pointed at an ongoing energy saving campaign, in which companies in Japan's northeast are being asked to cut back use by 15 percent, and argued that, if it works, it proves that Japan can live without atomic power.
The newspaper suggested in its editorial: "How about setting a target of reducing (atomic power) to zero within 20 years, to urge people to make their utmost efforts, and to review the plan every few years?"
Copyright AFP (Agence France-Presse), 2011