A U.S. expert on energy has raised concerns that North Korea’s non-military industries could suffer in the wake of the North’s active exports of minerals to China.

Nathaniel Aden, a researcher at University of California in Berkeley, made the remark in a report on North Korean and Chinese trade.

Aden said whereas North Korean electricity and iron ore exports are sold at sub-market “friendship prices,” Chinese coal and oil products have been sold to North Korea at premium prices.

He said that between 2000 and 2009, North Korean imports of Chinese merchandise stood at one-point-nine billion dollars, while the North’s exports to China amounted to 790 million dollars. The resulting trade deficit was around one-point-one billion dollars.

Aden added that the annual value of total bilateral trade between the North and China has grown from a 14-year low of 370 million dollars in 1999 to two-point-seven billion dollars in 2008.