Can I go back to US on old unexpired visa after getting new I797?

[anm9up]

My visa expires in Jan 2013. My company extended it by 3 yrs to 2016. Unfortunately I havent managed to get a visa stamping yet due to all sort of issues.

Will it be ok for me to go back to US on old unexpired visa? Or is it mandatory to get stamping once you get an I797 extensions. Also is there a minimum time limit for visa to be valid before flying to US? (I only have a month left)

Thanks in advance

[t75]

You may travel with the proper supporting documents. One day before expiration if you have valid reason for entry.