NEW YORK – McDonald's says a key sales figure dropped again in January as the world's biggest hamburger chain faced ongoing weakness in Japan and sales in China were hurt by a food scare and the timing of a holiday.

The Oak Brook, Ill.-based company said global sales at restaurants open at least 13 months dropped 1.9 percent for the month. The figure is a key metric because it strips out the volatility of newly opened and closed locations.

After years of outperforming rivals, McDonald's has been struggling amid intensifying competition and challenging economic conditions around the world. Late last year, the company ousted the head of its U.S. business after the sales figure dropped for the first time in nearly a decade. CEO Don Thompson, who took the top spot this summer, has vowed to add business by emphasizing value while planning a series of new limited-time offers to attract customers.