The U.S. special envoy for North Korean human rights has said China should abide by international commitments when dealing with North Koreans within its borders and that the plight of the refugees is among his highest priorities. The envoy is attending a conference on the North Korean human rights situation.

U.S. special envoy Jay Lefkowitz told the international conference Friday that North Korea is "a hidden world of hopelessness and terror".

North Korea has one of the worst human rights records in the world. The United Nations says the Pyongyang regime uses public executions and forced labor camps to quash dissent, and human trafficking is widespread in the Stalinist nation.

The United States estimates as many as 50,000 North Koreans have fled to China to escape hunger and persecution, but Mr. Lefkowitz said China is failing to address their basic rights. "There are international obligations that China has taken on," he said, "and we [the U.S. government] call on them, and expect them to live up to those obligations."

Mr. Lefkowitz says Beijing should give the United Nations High Commissioner for Refugees access to North Koreans in China, so they can be resettled in other countries.

However, China denies it has international obligations towards the North Koreans, calling them illegal economic migrants rather than refugees. The Chinese government returns many of them home involuntarily, where they face severe punishment or death.

Mr. Lefkowitz also says South Korea and the United States agree the human rights situation must change in North Korea, though he acknowledges the two nations have different approaches to bringing that about.

South Korea pursues a policy of gradual change through engagement with the North, and says it is counterproductive to confront Pyongyang on human rights issues.

Seoul has refused to vote on three United Nations resolutions calling for the North to act on human rights. Mr. Lefkowitz said Friday he hopes this policy will change.

However, the envoy praised South Korea for providing a home to about 6,000 North Korean defectors. "I commend the Republic of Korea on having taken in a number of refugees already," said Mr. Lefkowitz, "and I am confident that they will continue to do, as well, in the future."

South Korea and China are both cautious about their North Korean refugee policies, fearing a flood of immigrants could destabilize their countries.