Sales at stores open at least 13 months fell 3.7 percent in August, the Oak Brook, Illinois-based company said in a statement today. Analysts estimated a 3.1 percent drop. McDonald's also said that supplier problems in China will reduce third-quarter earnings per share by 15 cents to 20 cents.

McDonald's, which has more than 14,200 U.S. locations, is facing challenges at home and abroad. Domestically, it's been relying on discounts, limited-time offers and remodeled stores in a failed attempt to reignite growth. In China, meanwhile, the company's meat supplier OSI Group LLC was investigated for changing the expiration dates on food, triggering shortages and a sales slump.