UPDATE 1-Comscore sees holiday online spending up 7-9 pct

* Preliminary outlook sees improvement for 2010 holiday

* Forecast could change if unemployment rises

NEW YORK, Oct 14 (Reuters) - U.S. e-commerce spending for the 2010 holiday season could be between 7 percent and 9 percent higher than last year, according to a preliminary forecast from comScore SCOR.O.

But the analytics firm cautioned that the rate of sales growth could be limited by any change in the unemployment rate, price inflation or deterioration in the stock market.

“If any of those weaken between now and the end of the shopping season, it’s almost unavoidable (that) we’ll get less spending than we’ve forecast,” said comScore Chairman Gian Fulgoni in an interview.

In November and December 2009, U.S. online sales rose 4 percent compared to the same period last year.

Earlier this month, the National Retail Federation forecast holiday retail sales, excluding online sales, to rise by 2.3 percent this year to $447.1 billion, compared with a rise of 0.4 percent last year.

The No. 1 online retailer, AMZN.O e-commerce company eBay Inc EBAY.O and websites run by chains such as Wal-Mart Stores, WMT.N the world's largest retailer, are gearing up for the holiday season, which can account for as much as 40 percent of annual sales.

Tepid growth in consumer spending has meant more competition, with retailers vying to undercut one another with perks like free shipping.

“It’s pretty clear that Wal-Mart doesn’t like being number two or three. They’ve publicly said that e-commerce is a strategic focus for them on a global basis. To what extent has Amazon’s success prompted that?” Fulgoni said.

Last holiday, U.S. online spending rose to $29.1 billion, beating comScore’s expectations, helped by pent-up demand following a dismal 2008 holiday season. (Reporting by Alexandria Sage and Phil Wahba. Editing by Robert MacMillan)