(Reuters) - Walgreen Co said on Thursday it plans to buy regional drugstores from Stephen L. LaFrance Holdings Inc for $438 million, giving the largest U.S. drugstore chain 144 stores in some smaller communities and a distribution center in Arkansas.

Walgreen also reported another month of disappointing sales at its existing stores, with June same-store sales down 10 percent and comparable pharmacy sales down 15 percent. Walgreen continues to see Express Scripts Holding Co patients go elsewhere after Walgreen and Express Scripts failed to reach terms for a new contract at the beginning of the year.

The acquisition of USA Drug, Super D Drug, May's Drug, Med-X and Drug Warehouse Stores comes weeks after Walgreen said it would take a 45 percent stake in Europe's Alliance Boots Holdings Ltd and possibly buy the rest of it in a few years.

The latest deal, which includes stores in Arkansas, Kansas, Mississippi, Missouri, New Jersey, Oklahoma and Tennessee, should close around September 1 and is not expected to have a material impact on this year's earnings per share, Walgreen said. The chains Walgreen is buying posted $825 million in sales in 2011.

(Reporting by Jessica Wohl in Chicago; Editing by Gerald E. McCormick)