U.S. retail sales rose 4 percent during the 2010 holiday season, and should rise 2.2 percent in the first quarter of 2011, research firm ShopperTrak said on Monday.

Foot traffic for November and December, the most important part of the year for retailers, was flat, ShopperTrak said on Monday at the National Retail Federation conference in New York.

ShopperTrak expects foot traffic -- customers in stores -- to be up 2.8 percent in the first quarter.

Separately, Moody's.com Chief Economist Mark Zandi on Monday forecast sales gains in 2011 and 2012 for retailers, and predicted the U.S. market gains would pick up speed.

The Standard & Poor's Retail Index <.RLX> was up 0.11 percent in morning trading on Monday, compared to the broader S&P 500's <.SPX> 0.26 percent decline.

(Reporting by Phil Wahba and Dhanya Skariachan; editing by Gunna Dickson)