Consumers are expected to take to the Web to get the best deals delivered in time for Christmas on Monday in what is expected to be the busiest online shopping day of the year, but it may not be all good news for retailers.
Analysts warn that the latest retail data show average spending over the Thanksgiving weekend is falling.
This year, more than 131 million Americans are expected to go online for the shopping extravaganza nicknamed "Cyber Monday," according to data published by the National Retail Federation, up from 129 million in 2012.
Consumers making the most of online deals—and the intense competition between retailers in the lead-up to Christmas— have also proved a boon for delivery firms, with courier FedEx expecting to ship 22 million packages worldwide on Monday.
(Read more: Retailers exporting this US staple: Black Friday)
One leading retail analyst said there was "lots and lots of impetus behind Cyber Monday."
"Everyone's just been paid, it's the final pay check that they can feasibly use to order online to guarantee delivery in time for Christmas and a lot of people have generally been in the stores for general Christmas shopping anyway," Bryan Roberts, retail insights director at Kantar Retail, told CNBC's "Worldwide Exchange" on Monday.
"That's on top of global newspapers being full of recommendations of decent gifts for friends and family."
Roberts expected over 110 million visits to e-commerce websites on Monday, following a record amount of shoppers over the Thanksgiving weekend in the U.S.
Since "Black Friday" last week (the day following Thanksgiving in the U.S. that traditionally kicks off the Christmas shopping season) the NRF estimates that $57.4 billion was spent by 141 million unique shoppers this Thanksgiving weekend.
Spending over the weekend is expected to have declined 2.9 percent, however, an NRF survey of 4,500 shoppers revealed.
Dana Telsey, chief executive of the consulting brokerage firm Telsey Advisory Group, told CNBC that the spending decline was in no small part due to retailers aggressively marketing deals before the Thanksgiving weekend had started.
"You had the promotions and advertising for it all starting way before last Thursday or Friday of Thanksgiving. Many of the deals started last Monday and Tuesday and I think just many of the consumers got washed out over the weekend."
(Read more: Online sales leadholiday rush before Cyber Monday)
Kantor's Roberts also remarked that although more people were shopping online, he expected the "Cyber Monday" trend of a large bout of e-commerce to dissipate over time.
(Read more: Online sales 'to hit £5 billion' this Christmas)
"A lot of e-commerce businesses or multichannel retailers have really improved their offer and made it more efficient—you no longer need three weeks to guarantee delivery before Christmas as many retailers offer same or next-day delivery."
As a result of better delivery choices, Roberts and other analysts believe next Monday could also be a mini "Cyber Monday" as shoppers became more relaxed about delivery fulfillment.
(Read more: Move over Cyber Monday: New top shopping day coming)
"Black Friday" is the latest American export to influence shoppers on the other side of the Atlantic too, analysts have noted. Global research group Experian expects visits to U.K. retail websites to reach 113 million on Cyber Monday, too.
Roberts expected online auction house eBbay, retailer Amazon and discount chain Argos to be the most visited websites on Monday. "What 'Black Friday' might be doing, as it gains traction in markets like the U.K., is to bring spending forward rather than it being incremental."
—By CNBC's Holly Ellyatt, follow her on Twitter .