China has expressed frustration with North Korea, with one official calling it a "spoiled child," at the same time as brushing off U.S. requests to choke off the flow of military technology from Pyongyang to Tehran that helps to sustain the regime, according to leaked U.S. diplomatic cables.

One of the latest batches of cables released by WikiLeaks also quotes a South Korean official speculating that China might be able to accept reunification under South Korea's leadership.

Another...