The head of the Nuclear Regulation Authority said Wednesday that nuclear power plant operators, rather than regulators, are the ones to blame for the prolonged safety review of reactors that started last July.

"We are working hard so that the assessment process will be carried out as swiftly as possible. When thinking who is to blame, delays are occurring because the response of operators (to the NRA's requests) has been slow," NRA Chairman Shunichi Tanaka told a news conference.

Earlier in the day, local business federations of the Kansai and Kyushu regions jointly urged the NRA to "more efficiently" conduct the review so that reactors will be allowed to restart, citing concerns over power shortages and rises in electricity bills to cover fuel costs for thermal power generation.