From Reuters via the New York Times (link):
China said on Friday that Taiwan remained the most important issue in its relations with the United States, days before President Hu Jintao heads to Washington.
Vice Foreign Minister Yang Jiechi also said differences on trade and economic policies, which are expected to dominate talks between Hu and President Bush, could be resolved and countered suggestions that China’s rapid rise posed a threat to the rest of the world.
Yang called ties between Beijing and Washington “one of the most important bilateral relationships in the world” and said differences over a ballooning trade gap and the value of China’s currency could be managed.
See also Wikipedia’s “cross-Strait relations,” “political status of Taiwan;” also Chinese government’s “white paper on Taiwan issue”
