Wal-Mart Stores Inc. on Thursday said it plans to boost the pay of its U.S. employees in the first half of the year to at least $9 an hour, $1.75 above today's federal minimum wage.

By Feb. 1, 2016, the retailer expects its associates to earn at least $10 per hour.

The news came as Wal-Mart posted its second straight quarter of same-store sales growth in the U.S. on an increase in traffic; however, the retailer also issued weaker-than-expected guidance for the year, in part on the higher pay for associates.

"These changes will give our U.S. associates the opportunity to earn higher pay and advance in their careers. We're pursuing a comprehensive approach that is sustainable over the long term," said Doug McMillon, Wal-Mart president and chief executive.

For the new year, the company said it expected to post earnings of $4.70 to $5.05 a share. Analysts polled by Thomson Reuters had projected earnings of $5.19 a share and $497.2 billion in revenue for the year.

The quarter, which included the holiday shopping season, was the company's second-straight period of growth in U.S. same-store sales, at 1.2%, including fuel, following several quarters of declines or flat performance. The company had expected same-store sales at U.S. locations to be flat or grow up to 1%.

The company has responded to dwindling traffic numbers with smaller store formats and investments in its online business. Traffic at U.S. stores rose 1.4%, reversing a trend of declining traffic at the company's big-box locations.

For the quarter ended Jan. 31, Wal-Mart reported earnings of $4.97 billion, or $1.53 a share, up from $4.43 billion, or $1.36 a share, a year earlier. The company said in November that it expected to post $1.46 to $1.56 a share in earnings for the quarter, a range that fell below analysts' projections at the time.

Total revenue, which includes membership fees and other income, rose 1.4% to $131.6 billion, below analysts' recent projections of $132.4 billion.

For the current quarter, Wal-Mart said it expected to post 95 cents to $1.10 a share in earnings.

Write to Michael Calia at michael.calia@wsj.com

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