Diana Farrell writes in Businessweek:

Even a 45% depreciation of the dollar against the yuan would not result in balanced U.S. bilateral trade with China. The cost advantage of most Chinese exports is simply too great to be eliminated by currency movements alone. Moreover, many of the goods that the U.S. imports from China are not manufactured domestically. Nor are they available in sufficient quantities—at least at the moment—from other low-cost markets.

To read more:

http://www.businessweek.com/globalbiz/content/aug2007/gb20070823_646159.htm