(Reuters) - Marlboro maker Philip Morris International Inc (>> Philip Morris International Inc.) said it will buy out billionaire Carlos Slim's Grupo Carso (>> Grupo Carso S.A. de C.V.) from their Mexican joint venture for about $700 million (462 million pounds).

Grupo Carso will sell its 20 percent stake in Philip Morris Mexico in a deal that the U.S. company said would add marginally to its earnings per share in the fourth quarter.

Philip Morris said the agreement was subject to final price adjustments based on the Mexican unit's performance over a period of time.

"We have benefited greatly from our partnership with Grupo Carso and we remain confident in our ability to excel in this important market in the years ahead," James Mortensen, Philip Morris International's president of Latin American and Canadian operations, said in a statement.

Philip Morris said its partnership with Grupo Carso spanned more than 30 years. Slim, frequently listed as the world's richest man, is a member of the U.S. company's board.

The JV holds nearly three quarters of the market share of Mexico's total tax-paid cigarette industry by volume and Marlboro is the leading brand in Mexico with a 53.6 percent share as of 2012, the company said.

Philip Morris shares were down 1 percent at $94.06 in morning trading on the New York Stock Exchange, while Grupo Carso shares were down 2 percent on the Mexican Stock Exchange.

(Reporting by Siddharth Cavale in Bangalore; Editing by Saumyadeb Chakrabarty)