Wal-Mart Stores' first quarter profit rose 1.1% as the world's largest retailer struggled with a sales slump in its namesake business.

The company, based in Arkansas, blamed a payroll tax increase, delayed tax refunds and bad weather for the profit and sales results that missed Wall Street expectations.

The company also offered a profit outlook that came below analysts' projections.

Wal-Mart said today that it earned $3.78 billion, or $1.14 per share in the quarter ended April 30. That compared with $3.74 billion, or $1.09 per share, a year earlier.

Sales for the three month period rose 1% to $113.43 billion.

The results fell short of Wall Street expectations for earnings of $1.15 per share on revenue of $115.78 billion.

Wal-Mart reported a 1.4% drop in revenue at stores open at least a year at its namesake business, its first drop in a year and a half.

Revenue at stores open at least a year is considered a key measurement for retailers because it excludes the effect of stores that open or close during the year.