(Reuters) - Procter & Gamble Co <PG.N> posted higher quarterly profit on Friday, as the world's largest household products maker tries to reignite growth in sluggish markets such as the United States while activist investor William Ackman pushes for improvements.

P&G, the maker of Pampers diapers and Tide detergent, earned $4.06 billion, or $1.39 per share, in the fiscal second quarter ended in December, up from $1.69 billion, or 57 cents per share, a year earlier.

(Reporting by Jessica Wohl in Chicago; Editing by Jeffrey Benkoe)