Hi, I am a Hong Kong citizen with a permanent 3*** ID and also a green card holder of the US. I am planning to travel to Hong Kong, but my passport expired a week ago. I HAVE to travel back within a month, and I will be able to re-new my passport before I come back to the U.S. Is it possible for me to leave the U.S. without a passport but just using my green card? Since I will not have a problem entering Hong Kong boarder with my Hong Kong ID, but I have an expired foreign passport and it might cause problem for me to board on a plane. Is there any document that I could apply to leave the USA?