It follows the arrival of a new leadership at the IAA, including Wally O'Brien, its New York-based director-general, and David Hanger, the publisher of The Economist, as world president.
Hanger denied the IAA's move away from a tripartite structure was a defensive measure: "In the past we've refused entry to the people we're now trying to attract. But brands aren't just built by a lot of ad people and we want our membership to reflect that."
Formed in 1938 to help drive American presence into emerging world markets, the IAA performs widely differing roles in the 95 countries in which it is established.
In many Third World countries it is often the sole champion of commercial freedom of speech. In more developed markets it concentrates on education and training.