China's worsening North Korean headache By Kosuke Takahashi TOKYO - The problem of China's intractable neighbor North Korea developing nuclear weapons could grow even worse for Beijing if the United States seeks United Nations Security Council sanctions against Pyongyang. Then what will China do? How will it vote? Will its problem with its old Korean ally become a Sino-US problem - or even crisis? A Chinese diplomat close to the talks, speaking on condition of anonymity, showed this correspondent four four-character Chinese idioms commonly used in North Asia and specifically used these days to describe North Korea's duplicity, especially with...