International Driver's Permit

An International Driving Permit (IDP) is a document recognized by many countries which allows the permit-holder to drive a private motor vehicle in that country. To be valid the IDP must be accompanied by a valid license from the home country. The document is slightly larger than a standard passport and is essentially a multiple language translation of the permit-holder's normal driver's license, complete with photograph and vital statistics. It is not, however, a license to operate a motor vehicle on its own.

Individuals can usually apply for an IDP in their home country prior to arriving in the US. 

http://en.wikipedia.org/wiki/International_Driving_Permit