Wal-Mart Stores Inc. (WMT), the world's biggest retailer, on Monday brightened its outlook for December sales at U.S. stores open at least a year, seeing sales up 3 percent bolstered by post-Christmas spending.

A week ago, Wal-Mart forecast same-store sales in December would be in the middle of a forecast growth range of 1 to 3 percent, with higher oil prices expected to crimp the spending of lower income earners during the big holiday shopping season.

But Wal-Mart said food and general merchandise sales beat expectations in the week ending Dec. 31 while gift card redemptions were significantly higher than a year ago and sales were strongest in the mid-west of the country.

"Sales for the past weekend were above our plan," Wal-Mart said in a weekly telephone recording updating its sales performance.

Last week Bentonville, Ark.-based Wal-Mart said sales on the Sunday after Christmas were above its plan.

Its shares, which more than tripled in value over the past year, rose about 2 percent to $101 on Nasdaq.

The brightened December outlook came after Wal-Mart began the holiday season with low expectations, saying it only expected sales to increase between 1 and 3 percent -- its lowest monthly sales forecast in 19 months.

The weak forecast came after November same-store sales (search) only rose 0.7 percent. Wal-Mart admitted a decision not to discount goods as heavily as usual on the day after Thanksgiving, one of the year's biggest shopping days, had backfired.

It promptly began cutting prices and embarked on various advertising campaign to promote its cheap prices.

Wal-Mart will report on Jan. 6 its final sales figure for the five-week period from Nov. 27 to Dec. 31.