Wal-Mart Stores today reported a third quarterly decline in US comparable sales in a row, as the world's largest retailer gave a disappointing profit forecast for the key Christmas season.

The company said comparable sales at its US stores, its biggest unit, fell 0.3% in the third quarter that ended on October 31. It partly blamed the drop on disappointing toy sales and price reductions on televisions.

Wall Street had expected no change in comparable sales, which include those online and at stores open at least a year. 

"Some customers feel uncertainty about the economy, government, jobs stability," the company's chief executive Mike Duke said.

He said that Wal-Mart expects US comparable sales to be flat during the current holiday quarter.

The company forecast a profit of $1.60 to $1.70 per share for that quarter, while Wall Street analysts were expecting $1.69, according to Thomson Reuters.

Wal-Mart lowered its full-year forecast and now expects earnings of $5.11 to $5.21 per share, compared with an earlier outlook of $5.10 to $5.30.

To compete against retailers such as Amazon.com and Target Corp, Wal-Mart began its Christmas sales earlier and is advertising more heavily. 

Overall revenue increased 1.6% to $115.69 billion, while Wall Street was expecting $116.8 billion. International sales rose 4.1% to $34.4 billion, excluding any currency impact.