* Nuclear energy to continue playing major role-PM
* Future energy plan must be reviewed from scratch-PM (Recasts, adds background)
By Chikako Mogi and Yoko Kubota
TOKYO, May 10 (Reuters) - Prime Minister Naoto Kan said on Tuesday that renewable energy would be a key pillar of Japan's new energy policy after the world's worst nuclear crisis in 25 years, but that it would still rely on nuclear power for much of its electricity needs.
Kan also said that Japan's basic energy plan to build new atomic reactors to increase the share of nuclear power in electricity supply in the future must be reviewed from scratch.
The massive earthquake and tsunami on March 11 knocked out cooling systems at the Fukushima plant in northeast Japan, and the prolonged crisis could hamper Japan's efforts to reduce its use of fossil fuels.
"The current basic energy policy envisages that over 50 percent of total electricity supply will come from nuclear power while more than 20 percent will come from renewable power in 2030. But that basic plan needs to be reviewed now from scratch after this big incident," Kan told a news conference.
"I think it is necessary to move in the direction of promoting natural energy and renewable energy," he said, citing wind, solar or biomass energy as possible alternative sources -- areas that Japan lag globally.
Japanese engineers are still trying to gain control of the Fukushima Daiichi plant, 240 km (150 miles) north of Tokyo, whose cooling system was knocked out after the massive quake and tsunami and four out of the six reactors at the plant remain volatile.
Unpopular Kan, under fire for his handling of the Fukushima crisis, last week called for Chubu Electric 's Hamaoka nuclear plant in central Japan to halt operations until it can be better defended against a major tsunami, and Chubu on Monday reluctantly agreed to this.
While some have lauded Kan's calls, several business leaders and media, which tend to be close to the politically influential nuclear power industry, have criticised his move as being too abrupt and lacking a sound explanation.
Kan defended his decision, saying that the request was made after careful deliberation.
Japan will need to conduct a thorough investigation into the nuclear incident, Kan said, adding he wants to call on the international community for safer use of nuclear power.
The prime minister, who is the fifth leader of Japan in as many years, is likely to speak about his country's atomic crisis at the Group of Eight summit at the end of May in France. (Editing by Michael Watson and Sanjeev Miglani)