American dairy marketing firm DairyAmerica will sell its products on Fonterra's auction site from early October.
The trading platform GlobalDairyTrade has grown since it started selling whole milk powder on a monthly basis three years ago, and now sells seven products twice monthly to about 350 bidders from 67 countries.
After finalising market rules for all participants last week, DairyAmerica will join as a supplier of skim milk initially to build up its export business.
The body, which represents four US dairy co-operatives, says the auctions site's acceptance by buyers, will aid the expansion of its export business.
Global DairyTrade general manager Paul Grave says having Dairy America join up is an important step for Fonterra and it plans to bring other sellers on board next year.