What would the ramifications be for a trade war between US and China?

There has been news of US discontent with China. Geithner seems rather unhappy with the low yuan. On the other hand, the Chinese are concerned about the value of US treasuries. The Chinese are also quite reliant on exports and would be unwilling to appreciate the yuan significantly.

If there is a trade war (define: growing protectionism that hinders trade between the two countries), what would the ramifications be on:

1. The US market (i.e. Dow and S&P 500)
2. The US economy
3. The Chinese markets (i.e. Shanghai Index and Hang Seng I know this is Hong Kong)
4. The Chinese economy

Note: Please do not flame. This is not a forum for racist or bigoted views regarding either the Americans or the Chinese. This is meant to be a purely academic discussion.