SAN FRANCISCO, Nov 24 (Reuters) - ComScore Inc said on Tuesday 24 November it expects U.S. holiday e-commerce spending to rise 3 percent and the analytics firm cited a positive start to the online holiday shopping season.

Total online spending for the two-month holiday period beginning in November should reach $28.8 billion, versus $28.0 billion in 2008, the company said.

In the 2008 holiday season, online spending fell 3 percent.

Retail stalwarts Amazon.com (AMZN.O) and Wal-Mart Stores Inc (WMT.N) have already begun a price war online, heavily discounting items like new books in an effort to grab market share during the holidays.

For the first 22 days of the November-December holiday spending season, U.S. consumers spent $8.21 billion online, up 2 percent from $8.03 billion over the year-ago period.

ComScore Chairman Gian Fulgoni said in a statement that the holiday shopping season had "gotten off to a positive start."

"Nonetheless, online spending this holiday season will likely be tempered by the stark reality of 10 percent unemployment and less disposable income in many consumers' wallets," he added.

Despite the improvement over last year, the results will be far below the double-digit growth rates of 20 percent or higher seen in previous years.

Many consumers choose to go online instead of into stores to compare prices, search out bargains and avoid trips to the mall.

Earlier this month, comScore said that third-quarter sales trends had mirrored last year's, with no growth. It said then that fourth-quarter results would be positive, driven merely by easier comparisons with the year-ago period and not because consumer spending was strengthening.

Last fall, consumers pulled back dramatically on spending amid an escalating global economic meltdown.

(Reporting by Alexandria Sage; Editing by Richard Chang) (([email protected], +1-415-677-3923; Reuters Messaging: [email protected])) ((See blogs.reuters.com/shop-talk/ for Shop Talk -- Reuters' retail and consumer blog.))