"We will redirect parts of LNG (liquefied natural gas) imports from third countries through late March to April to Japan," an official at Knowledge Economy Ministry told AFP. Japanese electricity operators on Saturday asked for Seoul's help with its gas supply, predicting it will take more than a month for Tokyo to offset shortages caused by damage to key nuclear power plants, the official said. Negotiations with exporting countries are underway but it is unclear how much gas will be diverted to Japan, the world's top LNG buyer.

"We will provide as much as we can without disrupting our own domestic needs," she said, adding Tokyo will later return the gas under the LNG swap deal with Seoul. South Korea, the world's second-largest buyer of LNG, has secured nearly 98 percent of its estimated needs this year through mid-and long-term contracts, the ministry said. Japan has announced a programme of planned power cuts starting Monday after the massive earthquake and tsunami tore through the northeast of the country, crippling nuclear power plants in the region. Prime Minister Naoto Kan said Sunday he had authorised the blackouts to prevent any sudden major supply disruption and appealed for public understanding.