What isn't Walmart (WMT) trying to do this holiday season to win against its online nemesis, Amazon (AMZN) ?  

The world's largest retailer said Monday it will kick off its Cyber Week deals the day after Thanksgiving. So much for Cyber Monday -- which this year falls on Nov. 28 -- being the unofficial start to a week of online-only, mouth-watering discounts. Walmart's new online Cyber Week sale begins at 12:01 a.m. on Black Friday, headlined by a Samsung 60-inch HD smart TV for $579, a savings of about $1,120.

Helping to make the early start to Cyber Week possible is Walmart's significantly expanded number of items available for sale on its Web site. The company now boasts more than 23 million items for sale, in large part spurred by more third-party sellers, up from 8 million a year ago.  

Walmart also will begin its traditional online-only sales on Black Friday three hours earlier than last year at 12:01 a.m. The retailer's door-buster deals on Thanksgiving will begin around 6 p.m. 

Meanwhile, Walmart has brought its A-game with product exclusives for holiday shoppers, too.

Walmart will have 400 exclusive toys available this holiday shopping season, about in-line with last year. The list of toy exclusives will be headlined by a pricey $398 Disney (DIS) battery-powered car for children. In electronics, the number of product exclusives will be slightly more than a year ago.

"[Product exclusives] gives us a way to compete with online," Steve Bratspies, Walmart's U.S. chief merchant, told TheStreet in an interview.

While Walmart has assumed the role of aggressor this holiday season, Amazon isn't exactly standing still. 

Amazon began to offer holiday deals on Nov. 1 in an attempt to cash in on consumers looking to complete their shopping early. Additionally, it plans to offer another round of discounts on Black Friday that will run until Dec. 22. The company promises that new deals will be available as often as every five minutes, and has suggested shoppers be on the lookout for the best discounts during its "Turkey 5." Those are the five days of shopping that starts on Thanksgiving Thursday and runs through Cyber Monday. 

And unlike Walmart, Amazon will have some help this holiday season drumming up sales from a special friend. 

Amazon for the first time will make more than 500,000 toys available to order via its digital assistant Alexa for the holidays. According to Amazon, a voice command such as "Alexa order Play-Doh" will search for the lowest-priced option on the retailer's Web site and then ship it via Prime.

The new capability -- which should free up time-starved parents from having to search for toys online or visit a store -- could give Amazon a major leg up this holiday season to toy-selling rivals such as Walmart, Target (TGT) and Toys R' Us that don't have voice-activated shopping assistants. Not to mention that the new option could help spur sales of the $179.99 Echo hands-free device ahead of the holiday season. Talk about a win-win for the online juggernaut.

Wall Street may be becoming a touch worried on how the battle for shopper dollars this holiday season will weigh on retailers' fourth-quarter profits. Shares of Walmart and Amazon have fallen about 0.5% and 7%, respectively, over the last month. The S&P 500 has tacked on about 2% during that stretch.   

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