Mitsui & Co. said Wednesday it has won an order with Hitachi Ltd. to build a coal-fired power plant for U.S. firm Mid American Energy Co. in the United States.

The deal, which was to be signed later in the day, is worth 120 billion yen and is the largest U.S. power plant project ever awarded to a Japanese company, Mitsui said.

The plant is scheduled to start operations in June 2007 and have generating capacity of 790,000 kilowatts. Construction work is to begin in September.

It will be one of the most advanced power plants in the U.S. and will use energy-efficient technology supplied by Hitachi, Mitsui officials said.