Japan on Friday said its industrial heartland must cut electricity use by 10 percent this summer as the country grapples with a power shortage in the aftermath of last year's Fukushima atomic crisis.

A week after ordering the restart of two nuclear reactors, ending a brief period without any atomic power generation, the government said the expected shortfall would not be quite as bad as earlier thought.

Prime Minister Yoshihiko Noda and other senior ministers had previously said they wanted a 15 percent cut in peak electricity usage in and around the industrial hub of Osaka in western Japan from July to September.

But the bringing back online of two idled reactors at Oi has eased the expected crunch. The reactors are due to begin generating power in late July.

A power-saving order was issued last year as nuclear plants began to be shuttered in response to public disquiet over the technology in the months following the tsunami-sparked meltdowns at Fukushima.

But the cuts sparked complaints from businesses and fears manufacturers would move production overseas.

Prior to the quake-tsunami sparked Fukushima crisis, nuclear power supplied a third of Japan's electricity needs. In the months since, power companies have been increasingly dependent on imported -- and expensive -- fossil fuels.

Policymakers fear Japan's electricity demand could outstrip supply as summer temperatures soar and air-conditioners get cranked up, a worry for companies already battling uncertain economic times both at home and abroad.