Japan's top trading house, Mitsubishi Corp, says lower commodity prices and labour problems at its Australian coking-coal subsidiary weighed on quarterly earnings.
Net profit slipped 15.2 per cent to Y98.14 billion ($A1.2 billion) in the three months to June from a year ago. Revenue edged down 0.8 per cent to Y4.8 trillion in the quarter, the company said.
Mitsubishi blamed the revenue drop on lower prices and falling output at the coal project amid the labour strife.
A strong yen and higher sales and administrative costs also weighed, it said in a statement.
The coal project, an alliance between Mitsubishi and BHP Billiton, has been beset by weather problems and a long-running dispute over wages and worker participation in business strategy.
The project, which is now operating at about 70 per cent capacity, is a major earnings driver for Mitsubishi.
The Japanese firm said the joint venture would likely reach a settlement with its workers this month and resume full operations around the end of September.
For the fiscal year to March 2013, Mitsubishi kept its forecast for a net profit of Y500 billion, up 10.2 per cent from the previous year.
Operating profit was forecast to soar 25.4 per cent to Y340 billion with revenue rising 4.3 per cent to Y21 trillion.