McDonald's Corp posted a lower quarterly profit on Tuesday as sales at the fast-food chain's established U.S. restaurants fell more than expected on fewer customers.

Sales at U.S. restaurants open at least 13 months in the first quarter fell 1.7 percent. This was lower than the average estimate of 21 analysts polled by Consensus Metrix, which forecast U.S. same-restaurant sales would decline 1.4 percent.

McDonald's has reported roughly two years of turbulent sales at established U.S. restaurants due to sluggish economic growth, stiffer competition and internal missteps that have complicated menus and slowed service. It has also had fewer customers come in.

Elsewhere, the world's largest fast-food chain by revenue fared better. Global comparable sales rose 0.5 percent worldwide last quarter, helped by gains in Europe, where they rose 1.4 percent, compared to forecasts of a 1.2 percent increase.

In the Asia Pacific, the Middle East and Africa (APMEA) region, same-store restaurant sales rose 0.8 percent, compared to analyst projections for a 0.5 percent increase.

Chief Executive Don Thompson said in a press release that he expects comparable sales in April to be "modestly positive."

The world's biggest restaurant chain by revenue said net income fell to $1.2 billion, or $1.21 per share, three cents below Wall Street estimates, according to Thomson Reuters I/B/E/S. That compares to a profit of $1.27 billion, or $1.26 a share, a year earlier.

(Reporting by Phil Wahba in New York and Lisa Baertlein in Los Angeles; Editing by Lisa Von Ahn and Sofina Mirza-Reid)