McDonald's Corp. posted second quarter earnings on Monday which saw a profit increase of 4 percent, but was below Wall Street expectations.

The Oak Brook-based burger giant reported earnings of $1.38 per share, up 5 percent from a year ago.  The world's largest burger chain also said July sales are expected to be relatively flat and warned of a tough year ahead.

McDonald's said global sales edged up 1 percent at restaurants open at least a year for the three months ended June 30. The figure rose by the same amount in the U.S., where the company has rolled out new menu items to cater to the ever changing customers' needs.

Revenue rose 2 percent to $7.08 billion. Analysts were looking for $7.21 billion. For the quarter, the company earned $1.4 billion, or $1.38 per share. That's up from $1.35 billion, or $1.32 per share, a year ago.

Meanwhile, same-store sales at U.S. restaurants open more than a year were slightly negative in June, according to Don Thompson in a conference call with analysts Monday. The estimate is expected to be flat in July globally.

"While the informal eating out market remains challenging and economic uncertainty is pressuring consumer spending, we're continuing to differentiate the McDonald's experience by uniting consumer insights, innovation and execution," Thompson said in the call.

The Golden Arches store erported its first monthly same store sales decline in nearly a decade in October. At the time, the company was criticized for weakness in its U.S. business as competition from Wendy's and Burger King has increased.

Since then, McDonald's has re-emphasized its Dollar Menu, and introduced a number of higher-margin items, like McWrap sandwiches and an Egg White Delight breakfast sandwich. U.S. same store sales have improved since spring, and many experts have turned their attention to other issues in international markets, where McDonald's does about 60 percent of its sales.