Indonesia is the world's top exporter of the fuel and the main supplier to China. A slowdown in the Chinese economy has seen demand fall, with coal stockpiles growing at its ports.
"We see we may not reach our target of 390-million to 400-million tons, and the chances are it will be the same as last year," Supriatna Suhala, executive director of the Indonesian Coal Mining Association, told Reuters.
Suhala said that Indonesia was in a better position than Australia or South Africa as its coal mines benefited from being close to cheap river transport and seaports.
"That's our competitive advantage," he said, adding that growing U.S and Canadian coal exports to Asia was a cause of the oversupply.