INVITATION LETTER FROM MINISTRY OF FOREIGN AFFAIRS-CHINA

Hi, I am M.Ali businessman in Pakistan and travelling PRC since long, this time I submit my application along with Invitation letter from PRC partner/supplier. Consulate ask me to submit also invitation letter from PRC Ministry of Foreign Affairs. Al though I have my trade license and past Chinese visa copies. When I contacted my PRC supplier. He told me that business license to be certified by Chinese Consulate in Pakistan. First if PRC Consulate Pakistan has to verify than why they asked to me arranged from PRC. Second if PRC Consulate in Pakistan has to verify than what is the procedure and what else documents are required for verification. Kindly help and provide me guideline.