Prime Minister Naoto Kan says Japan should try to phase out its use of nuclear power following the disaster at the Fukushima nuclear plant.
An earthquake and tsunami on 11 March wrecked the plant, which continues to leak radioactive material.
Nuclear reactors produced 30% of the country's power before the disaster.
Mr Kan gave no time-frame, but said he is convinced that nuclear energy cannot be kept safe by conventional methods.
The BBC reports a large section of public opinion has turned against nuclear power.
In a televised news conference on Wednesday, Mr Kan said Japan should aim to develop alternative energy sources such as solar, wind and biomass.