TOKYO — Japan will develop and promote new clean energy technologies after the nuclear crisis, new foreign minister Koichiro Gemba said on Monday.

"We have bullet trains and water. From now on, there will be environmental technology," said Gemba, signalling a shift away from nuclear power, a technology the country has previously exported.

The minister, whose constituency Fukushima is at the centre of the ongoing atomic crisis, said new developments would include state-of-the-art solar batteries, which could replace nuclear reactors in the future.

"I'm sure it will be Japan's strong field. We will promote it through economic diplomacy," he said.

Last year, Japan agreed with Vietnam to jointly build two nuclear reactors in the Southeast Asian nation as part of a policy of "economic diplomacy" promoting exports of nuclear power technology.

"We will maintain (nuclear) technology, but I doubt it will be Japan's leading field of earnings in the future," Gemba said.

Prime Minister Yoshihiko Noda has said it will be "difficult" to build new reactors following the disaster but offline units should restart if deemed safe.

The surging waves triggered by the March 11 quake crippled backup cooling systems at the Fukushima Daiichi nuclear power plant, which led to reactor meltdowns, explosions and the release of radiation into the environment.