BEIJING/SEOUL: Coal shipments from the Democratic People's Republic of Korea (DPRK) to China have risen steadily this year, hinting at a deepening barter trade that makes it more difficult for the international community to apply pressure.

The DPRK's neighbors and the United States have been tightening sanctions to bring the country back to the negotiating table .

Chinese trade data for June showed no cut-off in normal trade shipments to and from the DPRK after a series of missile and nuclear tests in May. Chinese experts argue that too strong a stance by China would lose it what leverage it has with its ally.