I have valid visa till 2013. Last year when I came to US, my passport was about to expire in Dec'2011 and hence I got my I-94 till Dec'2011. Now I have renewed my passport. At the time of entry, the officials said I can apply for extension once I renew my passport. I saw your previous comments "legality of stay in USA is governed by your I-94, not the visa." So my question is how to do L-1 extension?
Two choices: Leave USA and reenter using your L-1 visa or re file your L-1 with USCIS for extension.