China to implement UN sanctions on N Korea

China has announced it will cut off imports of North Korean coal, iron ore and other key goods in three weeks under UN sanctions imposed over the North's nuclear program.

China, the isolated North's main trading partner, has been reluctant to push leader Kim Jong-un's regime too hard for fear it might collapse. But Beijing is increasingly frustrated with Pyongyang and joined in approving a UN Security Council ban on August 5 on coal and other key goods.

The Chinese customs agency said on Monday it will stop processing imports of North Korean coal, iron and lead ores and fish at midnight on September 5.

The latest sanctions are intended to block exports valued at more than $US1 billion ($A1.3 billion) - a significant loss to total exports valued at $US3 billion last year.

China is North Korea's largest trading partner, accounting for 90 per cent of North Korea's total trade.