RAK2013

Hi, Reply from "pontevecchio" shows for the people who changes employer in USA itself. My Doubts are: I have a H1B petition and Visa both valid till 30.09.2013. And now i got an offer from a company which is in USA. I got a new petition also. I have never used my current visa. (I am changing directly to USA company without using my current visa). My Visa is valid for two more months only. Can I travel with current visa and new petition like normally people change job in USA?? If I go for new stamping what are the risks involved?? If I travel with old visa when should I apply for extension?? Should I keep any validity in visa before applying for extension?? I got this doubt because I have never travelled to USA and changing job directly to USA. Your suggestion are welcome