Passport validity

I have an American passport that expires 14 Mar 2014, and on that passport, I currently have a tourist visa good for 2 entries for 6 months, between Aug 2013 and Feb 2014. My first trip is to Xian 19-21 Sep 2013, and my 2nd trip is to Harbin 17-21 Jan 2014. Will the passport be valid to use for both my trips? Or will there be any isues? Do I need to get a new passport before my 2nd trip? If so, will my visa carry over for use if I have to get a new passport? Thank you.