I am currently working in South Korea for a short time and have a 6 month visa and alien registration card.

I am currently working in South Korea for a short time and have a 6 month visa and alien registration card. At the end of my trip, I want to travel to China for a week then return to the U.S.A.

I spoke with a travel agent and they told me that since my South Korean visa is not longer than 6 months I cannot receive a Chinese visa. Is this because I am applying from South Korea? If I were to send my passport back to the U.S.A. and apply for a Chinese visa there will it be valid? What can I do to visit China?