- Andrew McMains

NEW YORK Susan Arnold, the highest-ranking woman at the world's largest marketer by spending, is leaving Procter & Gamble after 28 years.

Arnold, 55, today stepped down from her role as president of global business units -- a post that she had held since July 2007.

She'll remain with P&G on "special assignment" until she leaves the packaged-goods giant on Sept. 1.

Arnold had been viewed internally as a candidate to succeed worldwide CEO A.G. Lafley, 61, along with worldwide COO Bob McDonald, 55. Typically, senior officers at P&G retire by the age of 65.

In her global business-units position, Arnold oversaw some 300 brands that generate more than $80 billion annually in sales. In its last fiscal year ended June 30, 2008, P&G spent an estimated $8.7 billion worldwide on advertising.

Arnold approved budgets and set profit and loss goals for P&G's three divisions: beauty and grooming, health and well-being and household care, whose vice chairmen reported to her. Those leaders will now report directly to Lafley, a company representative said.

As such, P&G does not plan to fill the position.

In a statement, Lafley credited Arnold with leading the "transformation of P&G into one of the world's leading beauty companies -- with vision, creativity, consumer understanding and game-changing innovation."

When Arnold became president of the P&G's personal beauty business in 1999, the company had just one billion-dollar selling brand -- Pantene. Today, there are eight such brands within the beauty and grooming realm, according to P&G.

Lafley added that Arnold has been "instrumental in the development of top talent throughout P&G and she has served as a role model and coach for women inside and outside" the company.

P&G's global stable of creative agencies includes Publicis Groupe units Saatchi & Saatchi, Leo Burnett and Publicis; Omnicom Group units BBDO and TBWA; WPP Group's Grey; and independent Wieden + Kennedy.

In the U.S alone last year, P&G spent $3.26 billion in major measured media -- down 8 percent from 2007's total of $3.56 billion, according to Nielsen Monitor-Plus. Those figures do not include online spending.