Currently Mitsubishi imports about 2 million tons of CSEC produced coal into Japan but has plans to increase this total in the future.

The two companies plan to work together to develop coal mines, both in China and internationally, and broaden cooperation in emissions credit trading, the treatment of wastewater from coal mines and the installation of energy efficient devices at mines.

Mitsubishi - which has purchased about 30 million shares in the Chinese firm for about 15 billion yen [$US131 million] - does not plan to enter into a cross-shareholding arrangement with the mining company.