WPP Group's MindShare has handled the business since 1998. Prior to that, media buying and planning was done in-house at WPP's Ogilvy & Mather, which has had the creative portion of the account since 1962.
MindShare is expected to defend the business, according to an executive familiar with the matter. MindShare did not return a call for comment.
The AmEx spokeswoman, Judy Tenzer, said a new agency is expected to be named early to mid-2004.
American Express spent $287 million in measured media in the U.S. in 2002, according to TNS Media Intelligence/CMR. Published reports put the value of the global account at $375 million.