Japan’s Economics Minister Seiji Maehara said on Friday nuclear reactors can be restarted if a new regulator deems them safe, throwing into confusion how the dozens of units idle since the Fukushima disaster could be used in future energy plans.

Maehara, whose ministry had led debate in the cabinet on energy policy, said a new law empowered the regulator to endorse bringing reactors back online. He said the idle reactors could be a key source of power generation for now, a notion certain to anger Japan's growing ranks of opponents of nuclear power.

"If safety is approved, such reactors would be considered as an important power source," Maehara, who also oversees national strategy, told a news conference. "We should rely on nuclear as an energy option for the time being."

But procedures for going ahead with restarts remain unclear.

The new nuclear watchdog, the Nuclear Regulation Authority (NRA), said this week it does not hold ultimate responsibility to authorise reactor restarts and is concerned solely with safety.

All 50 working commercial reactors in Japan were taken offline for safety checks following the earthquake and tsunami that triggered meltdowns at the Fukushima Daiichi plant in the worst nuclear accident in a quarter of a century.

Two units were brought back online after receiving an endorsement from now defunct regulatory bodies, but the final decision on restarting them was taken by Prime Minister Yoshihiko Noda and three other ministers.

The restart of those reactors at the Ohi station in western Japan, to fend off possible summer power shortages, galvanised anti-nuclear protesters, leading to mass demonstrations in Tokyo and other cities.

Any further restarts would not come until next year. The NRA has said it will compile a blueprint of new standards to govern restarts by next March and subject to public discussion.

Noda's cabinet last month took account of anti-nuclear sentiment in devising a new energy policy that sought to end reliance on nuclear power by the 2030s by fostering renewable energy sources and supporting energy conservation.

But powerful industry lobbies have called for a rethink of policy and within days ministers appeared to waver on the commitment, saying other factors had to be considered before moving towards abandoning nuclear power within that time frame.