WPP's MindShare network has handled the business since its formation in 1997. Ogilvy & Mather's media department handled the business for more than 30 years before this.
The UK media planning and buying, which is held by Carat, is not currently part of the review. Carat won the UK business in 1992.
American Express expects to appoint an agency in the first half of 2004, with MindShare expected to defend the business.
It is holding the review to ensure that it keeps pace with changes in global media.
The global creative account, handled by Ogilvy & Mather, is not up for review.