The head of Japanese utility Kansai Electric Power Company Monday urged the prime minister to quickly decide on restarting two nuclear reactors at its Oi plant to avoid summer power shortages.

"The final decision rests with the government or the prime minister," Makoto Yagi told reporters, complaining of political delays.

"I ask that the prime minister make a bold decision quickly," he said, according to comments reported by local media.

Prime Minister Yoshihiko Noda, meanwhile, told a group of reporters that "the time for the decision is close," which he had already said two weeks earlier.

All of Japan's 50 nuclear reactors have been switched off, either because of earthquakes or for regular maintenance and none can be reactivated without passing tests of their ability to withstand natural disasters and without the consent of the local authorities and the government.

Town councillors in Oi, in the central prefecture of Fukui, on May 14 approved restarting reactor units No. 3 and 4 at the plant operated by Kansai Electric but it is up to Noda to give the final green light.

The policy decision is difficult as last year's tsunami-sparked meltdown at the Fukushima Daiichi plant has generated anti-nuclear sentiment among a wary public.

Kansai Electric, which relied on nuclear plants for half of its electricity output before the disaster, warned that its current capacity is likely to be 15 percent below demand this summer.

The government has appealed for companies and individuals to cut their power use but the company said this was not likely to be enough in very hot weather because of the heavy use of air conditioners.

Japan's other power firms, including Tokyo Electric Power (TEPCO), which operates the Fukushima plant, have also lost the use of their reactors and face some difficulty in meeting peak demand between July and September.