From The Japan Times Online :

In very important negotiations, the Chinese tend to work things in a manner different from the West. Their diplomats generally dislike framing positions in an edgy, confrontational, take-it-or-leave-it style. That approach strikes them as too risky. They tend to process an initial rebuff or outright rejection as engendering a loss of face, especially if they are committed to the negotiating framework.

Let us not forget that the six-party talks were China’s idea and that they have been hosted in Beijing.