NEW YORK — McDonald’s Corp. says a key revenue figure came in flat in July, its worst showing in more than nine years, as diners pulled back amid a rough economy. The snag also suggests competition is intensifying for the world’s biggest hamburger chain.

The last time the global sales figure fell for McDonald’s was in April 2003. The figure had grown every month since then, even in the recession.

‘‘McDonald’s may be underperforming the industry, which is not typical for them,’’ said Sara Senatore, a Bernstein analyst. She noted that Taco Bell is showing strength, and Burger King Worldwide Inc. and Wendy’s Co. are revamping their menus and stepping up their marketing.

In the United States, McDonald’s said its promotions failed to drive growth in July, and revenue at restaurants open at least 13 months fell 0.1 percent. The figure fell 0.6 percent in Europe and 1.5 percent in the Asia Pacific, Middle East and Africa region — a key growth area for McDonald’s.

Sales in Latin America and Canada, which are not reported separately, helped pull overall results even with last year.

Analysts polled by Thomson Reuters had expected growth of 2.8 percent in July.

McDonald’s plans to restart growth in the United States with variety and new menu items.