Retailers faced an uncertain 2006 Thursday after December’s modest sales gains showed that the holiday shopping season, while overall respectable, was disappointing for some of the nation’s most prominent merchants.

As expected, Wal-Mart Stores Inc. was one of the stragglers, falling short of Wall Street’s expectations and warning about its fourth-quarter profits.

Gap Inc., Sears Holdings Corp. and Kohl’s Corp. were among the other disappointments – as was Payless ShoeSource, whose same-store sales dropped by 1.5 percent, missing analysts’ forecasts for a gain of 3.2 percent.

Winning retailers included Target Corp., Costco Wholesale Corp., upscale stores such as Nordstrom Inc., and teen retailers like Abercrombie & Fitch Co.

A UBS-International Council of Shopping Centers retail sales tally posted a modest 3.2 percent sales gain, at the midpoint of the 3 percent to 3.5 percent growth forecast for the month.