If in transit at Shanghai airport for 50 hours do i need a visa to visit or stay in city hotel

arriving in Shanghai on 7th june 2013 at 11am by china Eastern airlines from new delhi my onward flight to san francisco,USA on china eastern airlines is after 50 hours that is on 9th june 2013 at 1pm in the afternoon.

I have confirmed seats on these dates and a valid passport

do i need one to stay in shanghai hotel for 2 nights and see the city or can i stay at Airport hotel like as if i am in transit and take a full one day city and sightseeing tour on 8th June 2013 and go straight to airport on 9th june from airport hotel.

i am a US citizen

Pls advise